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HANDBOOK 

FOR 

HEATING  AND  VENTILATING 
ENGINEERS 


BY 
JAMES  D.  HOFFMAN,  M.  E. 

PROFESSOR   OF    PRACTICAL   MECHANICS  AND   DIRECTOR   OF   THE 

PRACTICAL    MECHANICS     LABORATORIES,     PURDUE     UNIVERSITY 

MEMBER  AND  PAST   PRESIDENT   A.    S.   H.   &  V.   E. 

MEMBER   A.    S.    M.   E. 


ASSISTED  BY 


BENEDICT  F.  RABER,  B.  S.,  M.  E. 

PROFESSOR  OF   MECHANICAL  ENGINEERING 

UNIVERSITY   OF   CALIFORNIA 

MEMBER   A.    S.    M.   E. 


FOURTH 


AND   RESET 

•*-      *        I  •".""' 


McGRAW-HILL    BOOK    COMPANY 

239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 
1920 


Engineering 

Library 


COPYRIGHT,  1910,  1913,  1920 

BY 

JAMES  D.  HOFFMAN 


First  Edition,  1910 
Second  Edition,   1913 
Third  Edition,  1917 
Fourth  Edition,  1920 


PREFACE:  TO  FOURTH  EDITION. 

Changes  in  the  art  of  heating-  and  ventilating-  buildings 
have  been  so  pronounced  in  the  last  few  years  that  it  has 
been  considered  advisable  to  entirely  reconstruct  the  Hand- 
book rather  than  to  make  additions  to  the  old  text.  The 
book,  therefore,  has  been  rewritten  and  reset  in  every  part. 
There  have  been  added  approximately  87  pages  consisting 
of  revisions,  extended  discussions  of  original  text  and  new 
subject  matter  not  before  considered.  Of  this  increase,  Chap- 
ter I  has  17  pages,  including  discussions  on  heat  applications, 
combustion  of  fuels  and  analysis  of  flue  gases;  Chapters  II, 
III,  IV  and  V  on  air  measurements,  heat  losses  and  furnace 
heating  have  19  pages  devoted  largely  to  extensions;  Chap- 
ters VI,  VII,  VIII  and  IX  on  hot  water  and  steam  heating 
have  28  pages,  increasing  the  original  text  of  this  part  by 
approximately  43  per  cent.  This  includes  descriptions  of 
modified  gravity  systems,  both  steam  and  water,  valves,  fit- 
tings and  piping  connections;  Chapters  X,  XI  and  Xll  on 
mechanical  warm  air  systems  have  10  pages  of  extensions, 
and  Chapter  XIII  has  4  pages  of  extensions  to  the  calcula- 
tions of  hot  water  and  steam  mains.  The  remainder  of  the 
book  is  in  substance  as  it  was  with  the  addition  of  Sugges- 
tions to  School  Districts,  4  pages,  Chapter  XVIII,  Suggested  Pip- 
ing Connections  for  Vacuum  System  Details,  3  pages,  Appendix  3, 
and  several  new  tables  on  pipe  sizes  for  hot  water  and 
steam  service. 

Especial  attention  has  been  given  to  the  simplification 
of  every  important  subject  by  applications  to  practical  prob- 
lems. These  applications  in  most  cases  have  been  completely 
analyzed  and  their  results  compared  with  other  parallel 
cases.  No  effort  has  been  spared  to  have  the  entire  subject 
matter  complete  and  up  to  date  and  to  present  it  in  a  way 
that  will  be  at  once  simple  and  effective. 

This  little  book  is  as  a  growing  child.  We  wish  it  to  be 
very  active  and  useful  to  the  general  public.  To  do  this  it 
must  be  versatile  and  resourceful,  carrying  no  excess  ma- 
terial and  trained  down  to  service  condition.  We  ask  the 
assistance  of  our  friends  and  their  suggestions  in  its  behalf. 

LaFayette,  Ind.  J.  D.  H. 

425899 


EXTRACT    FROM    PREFACE    TO    FIRST    EDITION. 

In  the  development  of  Heating-  and  Ventilating  work,  it 
is  highly  desirable  that  those  engaged  in  the  design  and  the 
installation  of  the  apparatus  be  provided  with  a  Handbook 
convenient  for  pocket  use.  Such  a  treatise  should  cover  the 
entire  field  of  heating  and  ventilation  in  a  simplified  form 
and  should  contain  such  tables  as  are  commonly  used  in 
every  day  practice.  This  book  aims  to  fulfill  such  a  need  and 
is  intended  to  supplement  other  more  specialized  works.  Be- 
cause of  the  scope  of  the  work,  its  various  phases  could  not 
be  discussed  exhaustively,  but  it  is  believed  that  the  funda- 
mental principles  are  stated  and  applied  in  such  a  way  as 
to  be  easily  understood.  It  is  suggestive  rather  than  diges- 
tive. The  principles  presented  are  the  same  as  those  that 
have  been  stated  many  times  before,  but  the  arrangement  of 
the  work,  the  applications  and  the  designs  are  all  original. 
Many  equations  and  rules  are  necessarily  given;  but  it  will 
be  seen  that,  in  most  cases,  they  are  developments  from  a 
few  general  equations,  all  of  which  can  be  readily  under- 
stood and  remembered.  Practical  points  in  constructive  de- 
sign have  also  been  considered.  However,  since  the  prin- 
ciples of  heating  'and  ventilation  are  founded  upon  funda- 
mental thermodynamic  laws,  it  seems  best  to  accentuate  the 
theoretical  side  of  the  work  in  the  belief  that  if  this  is  well 
understood,  practical  points  of  experience  will  easily  follow. 

All  the  standard  works  upon  the  subject  have  been 
freely  consulted  and  used.  In  most  cases  where  extracts  are 
made,  acknowledgment  is  given  in  the  text.  Because  of 
these  references  throughout  the  book,  we  do  not  here  repeat 
the  names  of  their  authors.  We  wish,  however,  to  express 
our  sincere  appreciation  of  their  valuable  assistance. 

LaFayette,  Ind.  J.  D.  H. 


EXTRACT    FROM    PREFACE    TO    SECOND    EDITION. 

A  few  corrections  were  made  on  the  first  edition  and  all 
the  material  has  been  revised  and  brought  up  to  date.  The 
work  on  air  conditioning-  has  been  amplified.  The  descrip- 
tions of  hot  water  and  steam  heating  have  been  improved 
by  diagrams  of  the  various  piping  systems.  Two  chapters 
have  been  added  on  refrigeration  and  many  tatfles  have  been 
added  in  the  Appendix.  Many  suggestions  coming  from  men 
in  practice  have  been  included,  thus  enlarging  upon  the  prac- 
tical side  and  the  applications. 

Lincoln,  Neb.  J.  D.  H. 


CONTENTS 


CHAPTER  I.      (Heat  and  Combustion) 

Arts.  Pages 

1-     8     Introductory.     Measurement  of  Heat  and 

Temperatures    9-   16 

9-   17     Discussion  of  Heat  and  Heat  Applications 17-   34 

CHAPTER  II.      (Air) 
18-   23      Composition"  of  Air.     Amount  required  per 

Person    35-   43 

24-   27      Humidity  44-   51 

28-   29     Convection  of  Air.     Measurement  of  Air 

Velocities    52-   56 

30-   34     Air  used  in  Combustion.     Chimneys.     Cowls..   57-   60 

CHAPTER  III.     (Heat  Losses) 
35-   42     Heat  Losses  from   Buildings   61-   73 

43  Temperatures  to  be  considered 73 

44  Heat  given  off  from  Lights  and  Persons 74 

45  Performance  to  Guarantee  Heating  Capacity  74-   75 

CHAPTER  IV.     (Furnace  Heating) 

46-   47     Essentials  of  the  Furnace  System  ." 76-  77 

48-   61     Calculations  in  Furnace  Design  77-  85 

62  Application  to  a  Ten  Room  Residence 86-  91 

63  Determination  of  Best  Outside  Temperature  92-  94 

64  Humidifying  Furnace  Air  95-  99 

CHAPTER  V.      (Furnace  Heating,  Continued) 

65-  66     Selecting,  Locating  and  Setting  the  Furnace  100-105 

67-   72     Air  Ducts.     Circulation  of  Air  in  Rooms 106-112 

73  Fan  Furnace  Heating  113-114 

74-   75     Hot  Air  Radiator  Systems  115-117 

76  Improving  Sluggish   Circulation   117 

77  Suggestions  for  Operating  Furnaces 118-119 

CHAPTER  VI.     (Hot  Water  and  Steam  Heating) 

78-   81     Comparison  and  Classification  of  Systems 120-125 

82  Diagrams   of   Piping   Systems   125-130 

83-   85     Modified  Gravity  Systems  130-140 

86  Standard  Piping  Connections  141-143 


CHAPTER  VII.     (Hot  Water  and  Steam  Heating,  Cont'd) 
Arts.  Pages 

87-   88      Heaters,  Boilers  and  Accessories  144-150 

89-   95     Classification  and  Efficiencies  of  Radiators.. ..150-157 

96  Pipe   and   Fittings   157-163 

97-   99      Expansion  Tanks,  Fire  Coils  and  Corrosion. ...163-165 

CHAPTER  VIII.     (Hot  Water  and  Steam  Heating,  Cont'd) 
100-104      Calculations  for  Boiler  Size  and  Radiator 

Surface    166-177 

105  Greenhouse  Heating  177-180 

106-107     Determination  of  Pipe  Sizes  180-184 

108-109      Pitch  of  Mains  and  Radiator  Connections 184-185 

110  General  Application  to  Hot  Water  Design 185-191 

111-112     Insulating  Steam  Pipes.     Water  Hammer 191-193 

113  Feeding  Return  Water  to  Boiler 193-198 

114  Hot  Water  Heating  for  Tanks  and  Pools 198 

115  Suggestions  for  Operating  Boilers 198-199 

CHAPTER  IX.      (Mechanical  Vacuum  Heating) 
116-117     General.     Return  line  and  Air  line  Systems 

Described    200-204 

118  Vacuum  Pumps  and  Regulation  205-208 

119  Vacuum  Specialties  208-212 

CHAPTER  X.      (Mechanical  Warm  Air  Heating) 
120-124     General  Discussion.     Blowers  and  Fans. 

Heating  Surfaces  213-223 

125-128     Single  and  Double  Duct  Systems.     Air 

Washing    223-233 

CHAPTER  XL      (Mechanical  Warm  Air  Heating,  Cont'd) 
129-133      Heat  Loss.     Air  Required.     Air  Tempera- 
tures      234-237 

134-135     Air  Velocities.     Area  of  Ducts 237-238 

136-140     Heating  Surface  in  Coils.     Arrangement  of 

Coils   238-247 

141-143     Amount  of  Steam  Used  in  the  System 247-248 

CHAPTER  XII.      (Mechanical  Warm  Air  Heating,  Cont'd) 
144-148     Air  Velocity  and  Pressure.     Horse-Power 

in  Moving  Air  249-260 

149-154     Fan  Sizes  and  Drives.     Speeds.     Size  of 

Engine.  '  Piping  Connections  260-266 

155-156     General  Application  to  Plenum  System 267-274 


CHAPTER  XIII.      (District  Heating) 

Arts.  Pages 

157-161     General.     Conduits.     Expansion  Joints. 

Anchors  275-289 

162-164     Typical  Design.     Heat  in  Exhaust  Steam 289-295 

165-168     Hot  Water  Systems.     General  Discussion 296-298 

169-171      Pressure  and  Velocity  of  Water  in  Mains 298-303 

172-176      Radiation  Heated  by  Exhaust  Steam 304-306 

177-182      Reheating  Calculations   306-312 

183-186     Circulating   Pumps.      Boiler  Feed   Pumps 313-318 

187-191     Radiation  Supplied  by  Boilers  and  Econ- 
omizers     .* 319-323 

192  Total  Capacity   of  Boiler  Plant 323-326 

193-195     Cost  of  Heating  from  Central  Station. 

Regulating  the  Heat  Supply  326-332 

196  Steam   System.     General  Discussion  332-333 

197-199      Pipe  Sizes.     Dripping  the  Mains  334-338 

200  General  Application  of  Steam  System  to 

District    338-340 

CHAPTER  XIV.      (Temperature  Control) 
201-204      General.     Johnson,  Powers  and  National 

Systems     341-349 

CHAPTER  XV.      (Electrical  Heating) 
205-207     Discussion  and  Calculations  350-352 

CHAPTER  XVI.      (Refrigeration) 

208-209  Discussion  of  Systems  „ 353-354 

210-211  Vacuum  and  Cold  Air  Systems  354-355 

212-213  Compression  and  Absorption  Systems 355-358 

214  Condensers   359-361 

215  Evaporators  361-363 

216  Pipes,  Valves  and  Fittings  363 

217-218  Absorption  System  364-367 

219-220  Generators    368-369 

221-225  Condensers,  Absorbers,  Exchangers  and 

Pumps    369-371 

226-227     Comparison  of  Systems  372 

228  Methods  of  Maintaining  Low  Temperatures. .373-374 

229  Influence  of  Dew  Point  375-376 

230-231     Pipe   Line   Refrigeration   376-377 


CHAPTER  XVII.      (Refrigeration,  Continued) 
Arts.  Pages 

232-234     Calculations  378-382 

235  General  Application    383-384 

236-238     Method  of  Rating  Capacity   384-385 

239  Cost   of   Refrigeration    385-387 

CHAPTER   XVIII.      (Specifications) 

Suggestions   on   Planning   Specifications 388-394 

Suggestions  to  School  Districts 395-398 

APPENDIX  I. 
Tables  1-57  399-452 

APPENDIX  II. 
Tables  58-75  453-463 

APPENDIX  III. 

Test  of  House  Heating  Boilers  and  Data 
Required  for  Estimating  Hot  Water  and 
Steam  Boilers  465-467 

Details  of  Vacuum  Piping  Systems 468-470 


CHAPTER  1. 


HEAT — ITS  NATURE,  GENERATION,  USE,  MEASUREMENT 
AND  TRANSMISSION. 


1.  Introductory: — In  all  localities  where  the  atmosphere 
drops  in  temperature  much  below  60°  Fahrenheit,  there  is 
created  a  demand  for  the  artificial  heating  of  buildings.  As 
the  buildings  have  grown  in  size  and  complexity  of  con- 
struction, so  also  this  demand  has  grown  in  extent  and  pre- 
ciseness,  with  the  general  result  that  out  of  the  open  fire 
place  and  iron  stove  there  has  developed  a  science  growing 
richer  each  day  from  inventive  genius  and  manufacturing 
technique — the  science  of  the  heating  and  ventilating  of 
buildings.  The  purpose  of  this  handbook  shall  be  to  out- 
line the  fundamental  principles  and  practical  applications  of 
this  science  in  its  various  branches. 

To  the  average  heating  engineer  it  may  be  that  the 
exact  nature  of  heat  itself  is  of  much  less  moment  than  its 
generation  and  transmission,  but  these  facts  should  be  im- 
pressed,— that  heat  is  one  form  of  molecular  energy,  that  it 
cannot  be  created  except  by  conversion  from  some  other 
form,  and  that  it  is  infallibly  obedient  to  certain  physical 
laws  and  principles  which  should  be  understood  and  used 
by  every  engineer. 

In  generating  heat  for  heating  purposes  the  almost  uni- 
versal method  is  combustion.  The  union  of  the  combustible 
content  of  such  substances  as  coal,  wood  or  peat  with  the 
oxygen  of  the  air  is  always  attended  by  a  liberation  of  heat 
derived  from  the  chemical  action  of  the  combination;  and 
this  heat  is  carried  by  some  common  carrier,  such  as  air, 
water  or  steam,  to  the  building  or  room  to  be  heated  where 
it  is  given  off  by  the  natural  cooling  process.  In  some  in- 
stances this  heat  is  converted  into  electrical  energy  which 
is  carried  by  wire  to  the  place  of  use  and  given  off  as  heat 
through  a  set  of  resistance  coils.  This  method  is  not  much 
favored  as  yet  because  of  its  inefficiency  and  the  resulting 
expense,  an  objection  which  does  not  hold  in  the  case  of 
water  power  installations  where  the  combustion  of  fuel  is 
entirely  eliminated. 


10  IDEATING  A'ND  VENTILATION 

*J.  **eni— -'^emiK'.-jituro:  — The  meaning  of  the  word  heat 
should  not  be  confused  with  that  of  the  word  temperature. 
Although  closely  related  they  are  far  from  being  inter- 
changeable. In  a  given  mass  of  any  substance,  except 
when  passing  through  a  change  of  state,  the  universal  law 
is  that  the  addition  of  heat  raises  the  temperature  and  the 
subtraction  of  heat  lowers  the  temperature  of  the  sub- 
stance. Heat  is  the  cause  and  temperature  is  one  of  the 
effects.  In  the  measurement  of  heat  the  most  commonly 
accepted  unit  in  practical  engineering  work  is  the  British 
thermal  unit,  abbreviated  B.  t.  u.  This  may  be  denned  as 
that  amount  of  heat  which  ivill  raise  the  temperature  of  one  pound 
'of  pure  water  one  degree  Fahrenheit  (See  definition  for  specific 
heat,  Art.  8).  This  unit  value,  the  B.  t.  u.,  measures  the 
quantity  of  heat,  while  the  temperature  measures  the  inten- 
sity or  degree  of  heat.  In  equal  masses  of  the  same  sub- 
stance the  two  are  proportional.  The  Fahrenheit  scale  is  the 
more  commonly  used  temperature  scale,  especially  in  steam 
engineering.  The  unit  of  this  scale  is  derived  by  dividing 
the  distance  on  the  thermometer  between  the  freezing  point 
and  the  boiling  point  of  water  into  180  spaces  called  de- 
grees, the  freezing  point  being  marked  32°  and  the  boiling 
point  212°.  All  temperatures  in  this  book,  unless  otherwise  stated, 
will  be  taken  according  to  the  Fahrenheit  scale  and  all  quantities 
of  heat  expressed  in  British  thermal  units. 

A  second  unit  of  quantity  of  heat  considerably  used  in 
scientific  research  is  the  calorie,  abbreviated  cal.,  and  defined 
as  that  amount  of  heat  which  will  raise  one  kilogram  of 
pure  water  from  17°  to  18°  centigrade.  The  centigrade  scale 
is  a  second  temperature  scale,  the  unit  of  which  is  derived 
by  dividing  the  distance  on  the  thermometer  between  the 
freezing  point  and  the  boiling  point  of  water  into  100  de- 
grees, the  freezing  point  being  marked  0°  and  the  boiling 
point  100°. 

It  is  often  found  desirable  to  change  the  expression 
for  temperature  or  for  quantity  of  heat  from  one  system 
of  terms  to  that  of  the  other.  For  this  purpose  the  follow- 
ing equations  will  be  found  useful: 

9  5 

F  =  —  C  +  32  and  C  =   (F  —  32)  —  (1) 

5  9 

where  F  =  Fahrenheit  degrees  and  C  =  centigrade  degrees. 
From   these   equations   it   may   be   seen   that   the   two   scales 


MEASUREMENT   OF   TEMPERATURE  11 

coincide  at  but  one  point,  --  40°.  For  conversion  of  the 
quantity  units  the  following1  may  be  used: 

\  British  thermal  unit  =   0.252  calorie. 
1  calorie   =    3.968  British  thermal  units. 

These  are  for  the  absolute  conversion  of  a  certain  quantity 
of  heat  from  one  system  to  the  other.  If,  however,  the  effect 
of  this  heat  is  considered  upon  a  given  weight  of  substance 
and  the  weight  also  is  expressed  in  the  respective  systems, 
the  following  values  hold: 

1  calorie  per  kilogram   —   1.8  British  thermal  units 
per  pound. 

1  British  thermal  unit  per  pound  =   0.555  calorie 

per  kilogram. 

For  conversion  tables  see  Marks'  Mechanical  Engineers' 
Handbook  or  Kent's  Mechanical  Engineers'  Pocket-Book. 

3.  Instruments  Used  in  Measuring  Temperature: — In- 
struments intended  to  indicate  degree  or  intensity  of  heat, 
i.  e.,  the  temperature  of  substances,  are  designed  upon  many 
different  principles.  Of  these  the  following  represent  the 
important  general  classifications: 

EXPANSION  OF  A  LIQUID  WITH  INCREASE  IN  TEMPERATURE. — The 
ordinary  mercury,  alcohol  or  ether-in-glass  thermometers  be- 
long to  this  great  class.  Mercury  thermometers  should  not 
be  used  to  register  temperatures  near  the  top  of  the  scale 
for  fear  of  rupturing  the  glass.  To  overcojne  this  difficulty 
some  thermometers  are  made  with  a  mercury-well  at  the 
upper  end  of  the  mercury  column.  The  objection  to  be 
offered  to  this  form  is  the  difficulty  of  completely  emptying 
the  upper  well  after  it  has  been  partially  or  wholly  filled 
with  mercury.  The  ordinary  mercury-in-glass  thermometer, 
either  with  or  without  the  upper  mercury-well,  should  not 
be  used  on  temperatures  above  600°  F.  because  of  the  fact 
that  mercury  boils  at  680°  F.  Mercury-in-glass  or  mercury- 
in-quartz  thermometers  have  been  used  up  to  1300°  F.  by 
compressing  into  the  space  above  the  mercury  some  neutral 
gas,  as  nitrogen  or  carbon  dioxide.  This  type,  however,  is 
open  to  the  objection  of  high  breakage  costs.  Due  to  the 
fact  that  mercury  freezes  at  — 38°  F.  it  cannot  be  used  for  low 
temperature  thermometers.  These  are  usually  made  with 
alcohol  as  the  liquid,  since  alcohol  freezes  at  — 170°  F. 

EXPANSION  OF  A  SOLID  WITH  INCREASE  IN  TEMPERATURE. — In- 
struments built  upon  this  principle  are  commonly  called  ex- 
pansion pyrometers.  Fig.  1,  a,  shows  such  a  pyrometer.  Inside 


HEATING  AND  VENTILATION 


the  stem  of  the  instrument  is  a  metallic  expansion  element, 
the  movement  of  the  free  end  of  which  operates  the  hand  on 
the  dial.  Such  an  instrument  may  be  used  up  to  the  lowest 
temperature  of  the  softening-  point  of  the  metals  in  the  stem. 
Ordinarily,  errors  of  2  to  5  per  cent,  may  be  expected  in  the 
temperature  reading. 


Fig.  1. 

FUSION  OF  CONES  OF  REFRACTORY  MATERIALS. — This  principle 
is  exceedingly  simple  in  application  as  shown  in  Fig.  1,  6. 
Several  of  a  series  of  cones,  varying  in  mineral  compositions 
and  hence  in  melting  points,  are  exposed  to  the  temperature 


MEASUREMENT  OP  TEMPERATURE         13 

to  be  measured  and  this  temperature  is  indicated  by  that 
cone  of  the  series  which  just  melts  or  softens  sufficiently  to 
lose  its  shape.  With  the  cones  is  furnished  a  table  of  tem- 
peratures for  comparison.  From  the  illustration,  the  tem- 
perature indicated  is  evidently  that  corresponding  to  cone 
number  08,  which  from  the  Seger  cone  table  is  1814°  F. 
Seger  cones  for  such  measurements  may  be  obtained  to  indi- 
cate temperatures  from  1094°  F.  to  2800°  F.  by  increments 
varying-  from  25  to  55  degrees. 

TRANSFER  OF  A  HIGH  TEMPERATURE  BODY  AND  ITS  HEAT  TO  A 
KNOWN  QUANTITY  OF  WATER. — This  is  the  principle  embodied  in 
all  pyrometers  of  the  calorimetric  type,  one  of  which  is  shown 
in  Fig.  1,  c.  A  thoroughly  insulated  vessel  contains  a  known 
quantity  of  water,  a  thermometer  and  a  stirring  device.  A 
ball  of  platinum,  copper  or  iron  of  known  weight  and 
specific  heat  is  exposed  to  the  temperature  to  be  measured, 
by  means  of  the  handle  shown  in  the  figure  or  by  a  small 
crucible.  When  the  ball  has  reached  its  upper  temperature, 
it  is  quickly  transferred  to  the  water  of  the  insulated  vessel 
and  the  rise  of  temperature  of  the  water  is  noted  from  the 
thermometer.  Upon  the  suppositions  that  all  the  heat  In 
the  ball  is  transferred  to  the  water  and  that  the  ball  and 
the  water  finally  reach  the  same  temperature,  the  assump- 
tion may  be  made  that  the  heat  gained  by  the  water  equals 
that  lost  by  the  ball,  hence  the  product  of  the  weight,  tem- 
perature rise  and  specific  heat  of  the  water,  divided  by  the 
product  of  the  weight  and  specific  heat  of  the  ball  gives  the 
drop  in  temperature  through  which  the  ball  has  passed. 
From  this  the  upper  temperature  reached  by  the  ball  may 
be  obtained  by  adding  to  the  temperature  drop,  the  final 
temperature  of  the  water  and  the  ball.  Let  s  =  specific  heat 
of  the  ball,  T  —  upper  temperature  of  ball,  m  =  weight  of 
the  ball,  t  and  t'  respectively  =  beginning  and  ending  tem- 
peratures of  the  water,  and  w  =  weight  of  the  water. 
Remembering  that  the  specific  heat  of  water  is  1,  we  have 
w  (*'  —  t)  =  am  (T  —  f )  whence  (2) 

w  (t'  —  t) 

T  =  +  f 

sm 

The  objections  to  this  method  of  temperature  measurement 
are  its  slowness  due  to  the  necessary  computations  and 
manipulations,  and  the  fact  that  considerable  error  may  be 
introduced  during  the  transference  of  the  ball  from  the 
heated  space  to  the  calorimeter.  When  this  method  is  used 


14  HEATING  AND  VENTILATION 

for  very  high  temperatures  the  ball  is  made  of  porcelain  or 
fire  clay. 

CHANGE  OF  RESISTANCE  OF  AN  ELECTRIC  CONDUCTOR,  OR  CHANGE 
OF  VOLTAGE  OF  AN  ELECTRIC  THERMO-COUPLE. — Instruments  built 
upon  either  of  these  two  electrical  principles  are  extremely 
delicate  but  give  very  accurate  results,  it  being-  possible  to 
determine  temperatures  up  to  2000°  F.  with  a  variation  of 
but  one  or  two  degrees.  For  practical  work  electric  pyrom- 
eters are  more  commonly  of  the  thermo-couple  type  (See  Fig. 
1,  (1).  To  the  right  is  shown  a  porcelain  tube  enclosing  a 
thermo-couple  of  two  dissimilar  metals.  If  this  tube  is 
subjected  to  the  temperature  to  be  measured,  the  potential 
generated  by  the  couple  upon  heating  is  proportional  to  the 
temperature.  Hence,  if  connected  to  a  voltmeter  as  shown 
at  the  left,  the  voltage  generated  may  be  indicated,  or  as 
is  usual,  the  temperature  may  be  read  directly  since  the 
scale  of  the  voltmeter  may  be  graduated  in  degrees  instead 
of  in  volts.  This  type  of  pyrometer  is  extensively  used. 
From  each  of  a  large  number  of  testing  points,  thermo- 
couple wires  may  be  brought  to  a  central  point,  where  by 
means  of  a  switch  the  temperature  at  any  couple  may  be 
instantly  observed  by  throwing  its  current  into  a  common 
voltmeter  or  temperature  indicator. 

Other  types  of  temperature  measuring  instruments  are 
designed  upon  the  principle  of  the  optical  pyrometer,  and 
the  gas  and  air  thermometers,  but  these  are  not  used  to  as 
large  an  extent  in  practice  as  are  the  five  above  mentioned. 

4.  Absolute  Temperature: — In  experiments  that  have 
been  carried  on  with  pure  gases  with  the  use  of  air  ther- 
mometers, it  has  been  found  that  gases  expand  or  contract 

1  1 

approximately  of  their  volumes  at  32°  F.   ( of  their 

492  460 

volumes   at  zero   F.)    per  degree   change   in   temperature,   or 
1 

•   of   their   volumes   at    zero    C.      From    the   same    line   of 

273 

reasoning,  by  cooling  a  gas  to  — 460°  F.  or  — 273°  C,  it 
would  cease  to  exist.  This  theoretical  point  is  called  the 
absolute  zero  of  temperature.  All  'gases  change  to  liquids 
or  solids  before  this  point  is  reached,  however,  and  hence 
do  not  obey  the  law  of  contraction  of  gases  at  very  low 
temperatures.  The  fact  that  air  at  constant  pressure 
changes  its  volume  almost  exactly  in  proportion  to  the  abso- 
lute temperature,  T,  (460  +  t,  where  t  is  temperature  Fahr- 


MECHANICAL   EQUIVALENT   OF   HEAT  15 

enheit)  gives  a  starting-  point  to  be  used  as  a  basis  for  all 
air  volume-temperature  calculations.  For  instance,  if  a 
volume  of  20000  cubic  feet  of  air  at  0°  is  heated  to  70° 
with  constant  pressure,  its  volume  after  heating-  will  be 
greater  in  the  same  proportion  as  its  absolute  temperature 

x  530 

is  greater;   that  is,  =   ;  x   =    23000   cubic  feet,  or 

20000  460 

an   increase  of  15   per  cent. 

5.  Gage  and  Absolute  Pressures: — Gage  pressure  is  the 
total  pressure  per  square  inch  in  a  container  minus  the 
pressure  of  one  atmosphere.  Thus  65  pounds  gage  pressure 
means  that  the  container  is  carrying  65  pounds  pressure  per 
square  inch  of  surface  above  the  pressure  of  the  atmosphere. 
Atmospheric  pressure  at  sea  level,  14.696  commonly  written 
14.7,  is  used  on  all  but  the  most  exact  calculations.  This 
pressure  becomes  less  as  the  elevation  rises  above  sea  level. 
As  a  general  statement  it  may  be  said  that  atmospheric 
pressure  reduces  l/2  pound  for  each  1,000  feet  above  sea  level 
(See  Table  8,  Appendix).  The  total  pressure  exerted  within 
the  container  is  therefore  65  +  14.696  =  79.696  at  sea  level. 
This  total  pressure  is  known  as  the  absolute  pressure  and 
when  stated  in  pounds  per  square  foot  of  area  is  called 
specific  pressure. 

0,  Mechanical  Equivalent  of  Heat: — By  experiment  it 
has  been  determined  that  if  the  heat  energy  represented  by 
one  B.  t.  u.  be  changed  into  mechanical  energy  without  loss, 
it  would  accomplish  778  foot  pounds  of  work.  Similarly,  one 
calorie  is  equivalent  to  428  kilogrammeters  of  work. 

7.  Latent  Heat,  Total  Heat,  Etc.: — Not  all  the  heat 
applied  to  a  body  produces  change  in  temperature.  Under 
certain  conditions  the  heat  applied  produces  internal  or 
molecular  changes  and  is  called  latent  heat.  Thus  in  a  nor- 
mal atmosphere  if  heat  is  applied  to  ice  at  the  freezing 
point,  no  rise  of  temperature  is  noted  until  all  the  ice  is 
melted;  and  again,  heat  applied  to  water  at  the  boiling 
point  does  not  raise  its  temperature  until  all  the  water  is 
changed  to  steam.  The  first  is  called  latent  heat  of  fusion, 
which  for  ice  is  144  B.  t.  u.  per  pound;  the  latter  is  called 
latent  heat  of  vaporization,  which  for  water  is  970.4  (Marks 
and  Davis)  B.  t.  u.  per  pound.  For  most  calculations  the 
approximate  value  970  may  be  used.  Consult  books  on  ther- 
modynamics for  further  discussion  of  latent  heat  as  com- 
posed of  internal  and  external  work  equivalents.  Sensible  heat 


16  HEATING  AND  VENTILATION 

is  that  heat  whose  addition  or  subtraction  can  be  detected 
by  a  thermometer.  As  applied  to  the  standard  steam  tables, 
this  is  equal  to  the  total  heat  above  32°  minus  the  latent 
heat  of  vaporization.  Heat  of  the  liquid,  as  applied  to  the 
standard  steam  tables,  is  that  quantity  of  heat  added  to  a 
pound  of  water  at  32°  to  bring  it  to  the  temperature  of  the 
boiling  point  at  any  given  pressure.  At  atmospheric  pres- 
sure this  is  180  B.  t.  u.  Total  heat  is  that  quantity  of  heat 
represented  by  the  sum  of  the  latent  heat  of  vaporization 
and  the  heat  of  the  liquid.  In  the  evaporation  of  water  at 
atmospheric  pressure  this  is  970.4  +  (212  —  32)  =  1150.4 
B.  t.  u.  Total  heat  is  different  for  all  pressures  at  which 
evaporation  takes  place.  Consult  Art.  14  and  Table  4,  Ap- 
pendix, for  latent  heat,  heat  of  the  liquid  and  total  heat  at 
different  pressures. 

Convenient  approximate  equations  for  latent  heat  and  total 
heat  are  those  quoted  by  Regnault. 

Latent  Heat  =   1092  —  .695  (t  —  32)  (3) 

where  t  —  temperature  at  which  the  steam  is  formed. 

Illustration.- — The  latent  heat  of  steam  at  a  temperature 
of  338°  (pressure  100  Ibs.  gage)  is  1092  —  .695  (338  —  32)  = 
879.3  B.  t.  u. 

Total  heat  —  1092  +  .305  (t  —  32)  (4) 

Illustration. — The  total  heat  above  32°  of  the  same  steam 
as  in  previous  illustration  is  1092  +  .305  (338 — '32)  =  1185.3. 

8.  Specific  Heat: — The  specific  heat  of  a  substance  is 
that  quantity  of  heat  added  to  or  subtracted  from  a  unit 
weight  of  the  substance  when  its  temperature  is  changed 
one  degree.  The  mean  specific  heat  is  that  quantity  of  heat 
added  to  or  subtracted  from  a  unit  weight  of  the  substance 
in  changing  through  any  given  number  of  degrees,  divided 
by  the  number  of  degrees  change.  For  illustration,  the 
specific  heat  of  water  that  has  been  considered  standard  for 
many  years  is  obtained  at  the  temperature  of  its  maximum 
density,  39.1°  F.  (4°  C.).  This  is  used  in  much  of  the  physi- 
cal and  scientific  calculations,  but  in  most  engineering  work 
the  tendency  is  to  take  the  mean  specific  heat  between  the 
temperatures  of  32°  F.  and  212°  F.  (0°  C.  and  100°  C.),  i.  e., 
the  heat  required  to  raise  one  pound  of  pure  water  from  32° 
F.  to  212°  F.  divided  by  180.  This  is  the  same  as  the  specific 
heat  of  water  at  62°  F.  and  agrees  with  the  accepted  value 
of  the  B.  t.  u.  Table  26,  Appendix,  gives  specific  heats  of 
substances. 


RADIATION  17 

9.  Radiation: — Heat  may  be  transmitted  as  a  wave  mo- 
tion in  the  ether  of  space.  In  this  way  the  heat  of  the  sun 
reaches  the  earth.  Heat  of  this  form,  usually  referred  to  as 
radiant  heat,  requires  no  matter  for  its  conveyance;  passes 
through  some  materials,  notably  rock  salt,  without  change 
or  appreciable  loss;  and  follows  the  laws  for  the  radiation  of 
light.  It  is  assumed  that  the  heat  received  by  the  atmos- 
phere is  obtained  through  contact  with  the  bodies  giving 
and  receiving  heat  and  that  little  is  obtained  directly  from 
the  radiant  ray. 

TABLE   1. 
Radiation  Constants,  Values  of  C 

Material  C 

Glass,  smooth  0.154 

Brass,  dull  0.0362 

Copper,  slightly  polished  0.0278 

Lampblack    0.154 

Wrought-iron,  dull,   oxidized   0.154 

Wrought-iron,  clean,  bright  0.0562 

Cast  iron,  rough,  highly  oxidized  0.157 

Lime  plaster,  rough,  white  0.151 

Slate    0.115 

Gold  plate,  shining  but  not  polished  0.082 

Clay  0.065 

The  capacity  that  any  body  has  of  absorbing  the  radiant 
ray  is  called  its  absorption  capacity.  Absolute  black  bodies 
theoretically  absorb  all  the  radiation  received  upon  their 
surfaces  and  have  an  absorption  capacity  of  1.  Bright  or 
polished  surfaces  have  a  reduced  absorption  capacity.  It  is 
also  understood  that  the  radiation  capacity  is  proportional  to 
the  absorption  capacity.  The  amount  of  heat  radiated  by  a 
substance  is  practically  independent  of  the  form  of  the  sur- 
face and  depends  upon  the  difference  of  temperature  be- 
tween the  radiating  and  receiving-  surfaces,  and  upon  the 
color  and  character  of  the  surfaces.  The  Stefan-Boltzman 
radiation  law  states  that  for  black  bodies  the  radiating 
powe'r  is  proportional  to  the  fourth  power  of  the  absolute 
temperature  of  the  body.  For  other  than  black  bodies  this 
law  is  also  approximately  true.  Let  R  —  area  of  radiating 
surface  in  square  feet,  H  =  B.  t.  u.  radiated  per  hour,  T  = 


18  HEATING   AND   VENTILATION 

absolute  temperature  of  the  substance,  and  C  =  a  constant; 
then,  H  =  CR  (T  -=-  100)*.  For  a  dead  black  body  C  =  .1618. 
Other  values  of  C  from  Hutte  are  shown  in  Table  1. 

Assuming-  in  general  that  radiating-  surfaces  for  heating 
systems  may  be  classified,  as  black  bodies,  the  amount  of 
heat  radiated  from  a  surface  R  having  an  absolute  tempera- 
ture T  to  surrounding  surfaces  having  an  absolute  tempera- 
ture T!  is 

H  =  C  R  [(?'  -T-  100)4  —  (Tl   -f-   100)4] 

Applications  of  the  theoretical  formula  of  radiant  heat  to 
practical  problems  in  general  give  very  unsatisfactory  re- 
sults. 

10.  Conduction: — This    method   of   heat    transmission    Is 
very   evident  to   the   senses.      If  a   rod   of  metal   is   heated   at 
one  end,  the  heat  is  transferred  or  conducted  along  the   rod 
by  molecular  action.      Conduction  being  essentially   the   way 
by  which  solids  transfer  heat,  it  is  of  special  significance  in 
the  calculation  of  heat  losses  through   the  walls  of  a  build- 
ing1.    The  coefficient  of  conduction  may  be  defined  as  that  quan- 
tity    of    heat    which    passes     through     a    unit     thickness    of 
substance  in  a  unit  of  time  across  a  unit  of  surface,  the  dif- 
ference  of  temperature   between   the   two   sides   of  the   sub- 
stance  being   one   unit   of  the   thermometric   scale   employed. 
The    amount    of    heat    conducted    through    a    material    in    a 
given  time  is  directly  proportional  to  the  difference  in  tem- 
perature   between    the    two    parallel    sides   of   the    substance 
and    inversely   proportional   to   the   thickness.     As   a   formula 
H  —  cfb  (ti  —  /»)  where  c  =  coefficient  of  conductivity,  b  =. 
thickness  of  material   in   inches,   and   t\   and   /«    =    respective 
temperatures.      Since    the    complexity    of    building    construc- 
tions  renders   it   impossible   to   reduce   all   conduction    losses 
to   losses   per   unit   thickness   of   the   structure,   the   term   rate 
of  transmission  may  be  used   instead  of  conductivity  and  may 
be  understood  to  include  combinations  of  conductivities  and 
thicknesses.       This     may     be     illustrated     by     the     ordinary 
framed  and  studded  wall  where  K  is  the  rate  for  the  com- 
bination   (See  Chapter  III). 

11.  Convection: — Gases    and    liquids    convey    heat    most 
readily  by  this  method,  which  is  fundamental  with  warm  air 
and  hot  water  heating  installations.      If  it   is  attempted   to 
heat  a  body  of  water  by  applying  heat  to  its  upper  surface,  it 
will  be  found  to  warm  up  with  extreme  slowness.     If,  however, 


WORK  AND  POWER 


19 


the  source  of  heat  be  applied  below  the  body  of  water,  it 
will  be  found  to  heat  rapidly.  What  actually  happens  is 
this:  water  particles  near  the  source  of  heat  become  lighter, 
volume  for  volume,  than  the  colder  particles  near  the  top, 
and  because  of  the  change  in  density  gravity  causes  an 
exchange  of  these  particles,  drawing  the  heavier  to  the  bot- 
tom and  allowing  the  heated  and  lighter  particles  to  rise  to 
the  top  thus  forming  circulation  currents.  This  process  is 
known  as  convection.  It  will  not  occur  unless  the  medium 
expands  upon  being  heated  and  unless  the  force  of  gravity 
is  free  to  establish  circulating  currents.  In  the  hot  water 
heating  system  (Fig.  2),  water  rises  by  convection  to  the 
radiators,  is  there  cooled  and  descends  by  the 
return  circuit  to  the  point  of  heat  application 
completing  the  circuit.  The  warm  air  furnace 
installation  works  similarly,  air,  however,  being 
the  heat-carrying  medium. 

12.  Work: — Work  is  the  overcoming  of  a  resist- 
ance along  a   line  of  motion.      It   is   the   product   of 
force   and   distance   and   is   independent   of   time. 
Assuming  the  pound  to  be  the  unit  of  force  and 
the  foot  to  be  the  unit  of  distance,   the   unit  of 
work    is    the    foot-pound.       To    lift    one    hundred 
pounds  one  foot  or  one  pound  one  hundred  feet 
would  cause  the  expenditure  of  one  hundred  foot 
pounds  of  work. 

13.  Power: — Power  and  work  are  closely  re- 
lated but  are   not   identical.     Power  is  the  rate  of 

-*wtf      doing  work  and  always  comprehends  the  element 
Fig.  2.          of   time.      The    unit   of   power,   called   horse-power, 
has  no  reference  to  the  power  of  the  horse  nor  to  the  boiler 
horse-power,  but  is  an  arbitrary  value  equivalent  to 
1  horse-power  — 
746  Watts  =   .746  K.  W. 
33000  ft.  Ibs.  of  work  per  min. 
4562.4  kilogrammeters  of  work  per  min. 
33000  -*-  778  =  42.416  B.  t.  u.  per  min.      . 
4562.4   -f-   428   =   10.66  cal.  per  min. 

If  100  cubic  feet  of  water,  weighing  62.5  pounds  per  cubic 
foot,  are  lifted  100  feet  per  minute  without  friction  loss,  the 
horse-power  is  (100  X  62.5  X  100)  -=-  33000  =  18.94. 

The   term   boiler  horse-power  is  equivalent   to   34.5   pounds 


20  TITRATING  AND   VKNTILATH  >X 

of    water    per    hour    evaporated    from    water    at    212°    F.    to 

steam  at  212°   F.     This  equals  970.4    X    34.5    =    33479   B.   t.  u. 

14.       Application    of    Heat    to     Solids    and    Liquids: — All 

matter  in  its  most  finely  divided  state  is  made  up  of  minute 
particles  called  atoms  which  are  drawn  together  by  a  force 
called  attraction.  This  attraction  is  lessened  by  the  applica- 
tion of  heat,  the  particles  tending-  to  separate  (substance 
increasing-  in  size)  until  such  a  temperature  is  reached  (a 
certain  amount  of  heat  is  absorbed)  when  the  attraction  is 
zero.  From  this  point  further  application  of  heat  will  cause 
repulsion  and  the  particles  will  fly  apart.  This  explains  the 
existence  of  the  three  states  of  matter;  solid,  liquid  and 
gaseous.  No  two  substances  act  exactly  alike  upon  the 
•addition  or  subtraction  of  heat,  but  practically  all  sub- 
stances under  certain  conditions  may  exist  in  any  one  of 
the  three  states.  The  exact  points  of  separation  between 
the  solid,  liquid  and  gas,  differ  very  much  in  different  sub- 
stances; but  regardless  of  this  fact,  each  substance  no  mat- 
ter what  its  state  may  be  solidified  by  cooling  or  vaporized 
by  heating.  The  amount  of  heat  that  may  be  carried  by 
any  substance  in  any  given  state  is  called  its  capacity  for  heat. 
When  solids  change  in  temperature  they  change  in  vol- 
ume in  practically  all  cases,  increasing  with  rise  of  tempera- 
ture and  decreasing  with  fall  of  temperature.  This  fact 
many  times  causes  considerable  annoyance  to  any  one  manu- 
facturing or  using  materials  of  construction.  Since  all 
metals  that  enter  into  engineering  construction  are  subject 
to  sudden  and  sometimes  very  extreme  changes  of  tempera- 
ture, it  is  frequently  necessary  to  put  in  compensating  de- 
vice~s  to  account  for  such  temperature  changes.  The  steel 
framework  of  a  building  for  example  is  subjected  to  ex- 
tremes of  summer  and  winter  temperatures,  causing  change 
in  the  building  size.  This  change  is  small,  but  during  the 
cold  weather  when  the  building  materials  have  a  slight  re- 
duction in  size,  the  steam  pipes  are  under  high  temperatures 
and  have  their  maximum  size.  During  the  summer  when 
no  heat  is  necessary,  reverse  conditions  exist.  In  high 
buildings  this  change  is  sufficient  to  demand  compensators 
or  expansion  joints  in  the  steam  lines,  otherwise  there 
would  be  contact  between  the  pipes  and  the  building  which 
might  be  sufficient  to  rupture  some  part.  Like  conditions 
exist  in  street  mains  (conduit  lines),  basement  mains  in 
buildings,  horizontal  connections  between  vertical  risers, 


APPLICATION  OF   HEAT   TO  LIQUIDS 


21 


riser  connections  between  floors,  boiler  pipe  connections, 
boiler  settings  in  brick  work  and  in  many  other  places 
around  the  heating  system  of  the  average  building. 

Sudden  changes  of  temperature  in  any  material  are  to 
be  avoided  when  possible.  This  is  especially  true  if  the 
materials  are  fastened  together  with  screws,  bolts  or  rivets, 
such  as  boilers,  heaters  or  piping  systems.  When  heat  is 
thus  applied  it  is  always  more  intense  at  one  place  than  at 
another  and  the  expansion  or  contraction  is  not  uniform, 
causing  unnecessary  stresses  and  many  times  leaks  and  rup- 
tures. The  force  exerted  by  heat  in  expanding  any  substance 
is  the  same  as  would  be  required  to  stretch  the  same  sub- 
stance an  equal  amount  by  mechanical  means  or  to  compress 
the  enlarged  piece  to  its  former  size. 

When  heat  is  applied  to  liquids,  the  phenomenon  of  ex- 
pansion is  apparent  as  in  solids.  One  notable  exception  is 
found  in  water  between  32°  and  39.1°  F.  as  will  be  seen 
later.  Since  water  is  the  liquid  universally  used  in  heating  systems, 


PerLJb.     Psrib.  Pound     I  Pound  of  Wafer 

^STATE  CH/JNQE  or  WATER  UHDER  ATMOSPHERIC 


Fig.  3. 

it  is  of  interest  to  study  its  characteristics  under  different  conditions 
of  heat.  Start  with  a  mass  of  one  pound  of  ice  at  some  tem- 
perature, say  25°  F.  (it  must  be  remembered  that  after  ice 
is  formed  at  32°  F.  it  may  be  cooled  to  any  temperature 
below  32°  by  the  continued  extraction  of  heat),  and  while 
heat  is  being  added  to  the  mass,  note  the  changes  taking 
place.  In  Fig.  3  EFGABK  is  the  temperature  curve,  LMNOC  is 
the  volume  curve,  the  ordinates  MM',  NN',  OD  and  BC  represent 


22  HEATING  AND  VENTILATION 

the  periods  of  change  of  state,  and  the  horizontal  line  at  the 
base  of  the  chart  L'C  represents  heat  units  added.  With  LU 
representing-  the  volume  of  a  pound  of  ice  at  any  tempera- 
ture (in  this  case  25°  F.)  heat  is  added  and  the  temperature 
curve  E  rises  to  F.  The  quantity  of  heat  added  is  found  by 
multiplying-  the  pounds  of  ice  (in  this  case  1)  by  the  specific 
heat,  which  for  ice  is  .504,  and  by  the  rise  in  temperature. 
The  addition  of  .504  B.  t.  u.  for  each  degree  rise  between 
25°  and  32°  gives  the  ice  (32  —  25)  X  .504  =  3.528  B.  t.  u. 
and  brings  it  to  the  temperature  of  the  melting  point.  While 
the  temperature  has  been  gradually  increasing  the  volume 
has  also  increased  slightly.  See  MM'.  More  heat  is  added 
and  the  ice  begins  to  melt  but  the  temperature  does  not 
rise  as  would  be  expected.  It  remains  constant  from  F  to  O 
until  all  the  ice  has  changed  to  water,  as  shown  by  the  line 
l/.V.  In  this  change  there  has  been  a  reduction  in  the  vol- 
ume of  the  mass  as  shown  by  the  dropping  of  the  line  MN. 
Notice  that  the  volume  of  the  water  is  taken  as  1  and  the 
volume  of  the  ice  at  32°  as  1.09.  This  explains  why  water 
allowed  to  freeze  in  a  pipe  often  causes  the  bursting  of  the 
pipe.  The  quantity  of  heat  absorbed  during  the  change  of 
state  from  ice  to  water  without  change  of  temperature  is 
found  by  experiment  to  be  144  B.  t.  u.  per  pound  and  is 
called  the  latent  heat  of  fusion.  Conversely,  in  the  reverse 
change  the  same  amount  of  heat  would  be  given  off.  So  far 
we  have  added  to  the  pound  of  ice  3.528  +  144  =  147.528 
B.  t.  u.  and  have  increased  the  temperature  only  7  degrees. 
From  this  point  GNN',  where  the  entire  mass  is  water  with  a 
volume  approximately  equal  to  1,  the  addition  of  heat  causes 
a  uniform  rise  in  temperature  along  OA;  also  a  slight  de- 
crease in  volume  along  MN  to  the  point  of  maximum  density 
39.1°,  where  the  volume  NN'  is  1,  and  from  here  a  uniform 
increase  in  volume  along  NO  until  the  temperature  has  risen 
from  39.1°  to  212°  and  the  volume  has  increased  from  1  to 
1.034,  with  an  addition  of  212  —  32  —  180  B.  t.  u.  To  arrive 
at  the  state  line  AOD  required  the  addition  of  3.528  +  144  + 
180  =  327.528  B.  t.  u.,  and  a  total  of  187  degrees  change. 
At  AOD  a  second  change  of  state  is  encountered.  970.4 
B.  t.  u.  (latent  heat  of  vaporization)  are  now  added  to  the 
pound  of  water  without  changing  its  temperature  and  the 
mass  has  a  uniform  change  of  state  from  water  at  212°  to 
steam  at  212°.  When  the  temperature  line  reaches  B  the 
volume  line  of  the  water  is  at  C,  indicating  that  all  the 


APPLICATION  OF   HEAT   TO   LIQUIDS 


23 


water  has  become  steam  at  atmospheric  pressure  and  now 
occupies  a  volume  DABC,  1650  times  the  volume  of  the  water 
that  produced  it  (compare  volume  ABCD  with  small  black 
volume  D).  The  pound  of  ice  has  now  received  327.528  + 
970.4  —  1297.928  B.  t.  u.  and  is  in  a  state  of  steam  at  atmos- 
pheric pressure  and  212°  temperature.  Any  further  addi- 
tion of  heat  to  this  steam  without  being  in  contact  with 
water  results  in  an  increase  of  temperature  along"  the  line 
BK  and  the  steam  is  said  to  be  superheated.  The  quantity  of 
heat  added  as  superheat  is  found  by  multiplying  the  pounds 
of  steam  (in  this  case  1)  by  the  specific  heat  and  by  the 
change  in  temperature.  For  steam  the  specific  heat  varies 
with  the  pressure.  A  fair  average  value  is  .48.  The  heat 
absorbed  for  any  degree  of  superheat  may  be  added  to  the 
1297.928  B.  t.  u.  thus  giving  the  total  heat  between  the  two 
extremes  of  temperature  and  pressure  selected.  Ordinarily 
heating  calculations  refer  only  to  saturated  steam,  i.  e.,  steam 
in  contact  with  water  and  superheating  need  not  be  con- 
sidered. 

By  the  use  of  Equations  3  and  4  and  the  steam  tables 
compare  results  by  filling  in  the  blank  table  the  values  for 
steam  at  10,  14.7,  50  and  100  pounds  absolute  pressure. 


Equation 

Table 

10 

14.7 

50 

100 

10 

14.7 

50 

100 

Heat  of  the  Liquid 

Latent  Heat 

Total  Heat 

Three  standard  tables  of  properties,  of  saturated  steam  are 
in  general  use,  Marks  and  Davis,  Peabody,  and  Goodenough. 
These  tables  check  each  other  closely  and  any  one  may  be 
recommended  (Table  4,  Appendix,  is  an  extract  from  the 
first  table). 

The  following  summary  of  directions  for  the  use  of  any  of  the 
steam  tables  gives  specific  equations  for  the  solution  of  al- 
most any  type  of  problem  using  any  vapor  table.  With  the 
nomenclature  of  Marks  and  Davis,  we  have: 


HEATING  AND  VENTILATION 


FOR   SUMMATION  ABOVE   32°    F. 


If  Quality 

is  100% 

If  Quality 

isX% 

If  Superheat  is 
D  degrees 

Total  Heat  of 
Formation.... 

Intrinsic  Heat 
of  Formation 
External  Work 
of  Formation 

H  —  h  +  L 
h  +  I 
(Apu)v 

h  +  xL 
h  +  xl 
(xApu)v 

H  +  CpD 
h  +  7  +  CpD—  (Apu), 
(Apu)r  +  (Apu)» 

FOR    SUMMATION   ABOVE    SOME    FEED    TEMPERA- 
TURE  =   t 


If  Quality 

is  100% 

If  Quality 

isZ% 

If  Superheat  is 
D  degrees 

Total  Heat  of 
Formation    

H  —  ht  or 

h  +  L  —  ht 

h  +  xL  —  ht 

h  +  L  +  CpD  —  ht 

Intrinsic  Heat  of 
Formation    

h  +  I  —  ht 

li  +  xl  —  h  t 

h  +  I  +  CpD  — 
(Apu)*  —  .ht 

External  Work  of 
Formation    

(Apu)v 

(xApu)v 

(Apu)r  +  (Apu), 

In  these  tables  the  subscript  v  refers  to  the  condition  of 
non-superheats,  while  the  subscript  s  refers  to  the  condition 
of  superheat.  In  the  term  Apu,  the  value  of  A  is  1/778,  p  — 
pressure  in  pounds  per  sq.  foot  and  u  is  the  increase  in  vol- 
ume in  cubic  feet  undergone  during  the  process  in  question. 
Some  vapor  tables,  (notably  Peabody's)  contain  columns  of 
Apu  worked  out  and  tabulated  while  with  the  use  of  other 
tables  it  is  necessary  to  calculate  the  values  of  the  Apu  terms. 

These  tables  emphasize  those  facts  the  neglect  of  which 
causes  perhaps  90  per  cent,  of  all  steam  table  calculation 
errors,  viz: 

x  cannot  affect,  as  a  factor  any  steam  table  value 
except  L,  I,  and   (Ajtu),-. 

The  vapor  tables  are  summations  above  32°  F.,  and 
for  heat  summations  above  any  other  tempera- 
ture, correction  must  be  made. 

The  external  work  available  during  formation  is  in- 
dependent of  the  feed  temperature. 

15.  Application  of  Heat  to  Gases: — Pressure-volume- 
temperature  changes  in  gases  may  be  found  from  ideal  laws 
which  apply  with  close  approximation,  or  from  actual  laws 
(modifications  of  the  ideal  laws)  designed  to  fit  actual  con- 
ditions. The  ideal  laws  are  much  more  easily  applied  and 


APPLICATION  OF  HEAT   TO   GASES  25 

give  results  that  are  close  to  average  practice;  consequently, 
they  are  used  in  most  engineering-  calculations.  Ideal  laws 
are  known  as  (1)  The  Law  of  Boyle  or  of  Mariotte,  (2)  The 
Law  of  Charles  or  of  Gay  Lussac. 

BOYLE'S  LAW. — When  the  temperature  of  a  given  weight  of  gas 
is  maintained  constant,  the  volume  and  the  pressure  vary  inversely. 
In  many  pressure-volume  applications  to  gases  the  tempera- 
ture change  is  either  zero  or  so  small  as  to  be  of  no  serious 
moment.  This  law  applies  in  such  cases.  Let  P,  PI,  P2, 
etc.,  —  absolute  pressures  in  pounds  per  square  foot,  and 
V,  Vi,  V2,  etc.,  —  volumes  in  cubic  feet  at  the  respective 
pressures,  then 

PV  =  Pi  TTi  =  P2  V2,  etc.  (5) 

In  other  words,  at  a  constant  temperature  the  product  of 
any  pressure  with  its  respective  volume  is  a  constant  quan- 
tity. Thus  if  100  cubic  feet  of  air  at  14.7  Ibs.  absolute  pres- 
sure be  changed  to  50  cubic  feet  without  change  of  tempera- 
ture, the  pressure  will  be  (14.7  X  100)  -f-  50  =  29.4  Ibs. 
absolute,  or  14.7  Ibs.  gage. 

CHARLES'  LAW. — When  gases  are  heated,  they  react  ac- 
cording to  the  Law  of  Charles;  i.  e.,  the  volume  of  a  perfect  gas 
at  constant  pressure,  or  the  pressure  of  a  perfect  gas  at  constant 
volume,  is  proportional  to  its  absolute  temperature.  As  before 
let  P  =  absolute  pressure  in  pounds  per  square  foot,  V  = 
volume  in  cubic  feet,  and  T  =  absolute  temperature,  then 

PV  PxFi  P2V2 

=  ==  ,  etc.       .  (6) 

T  TI  T2 

Referring  to  the  first  part  of  the  definition  of  this  law,  let 
the  temperature  of  a  cubic  foot  of  gas  (take  air  for  illus- 
tration at  atmospheric  pressure)  be  32°  F.,  if  f  —  32  + 

PV 

460  =  492,  P  =   14.7   X   144  =  2116.8  and  V  =   I,  then  - 

T 
2116.8  X  1 

— • .     Now  if  the  temperature  of  the  air  is  changed  to 
492 

some  other  temperature  Tlt  say  100°  F.  at  the  same  pressure, 
PV  P!  F! 

— •  and,  since  PI  —  P,  the  new  volume  is 

T  T! 

2116.8  X  1  560  560 

Tt  =  : X-  =  1.14  V 

492  2116.8  492 

Referring  to  the  second  part  of  the  definition  of  the  same 
law,  take  a  cubic  foot  of  air  at  atmospheric  pressure  and 
32°  F.  and  change  its  temperature  to  100°  F.  while  the  vol- 


26  HEATING  AND  VENTILATION 

ume  remains  constant  at  one  cubic  foot.  Now,  the  pressures 
at  constant  volume  are  proportional  to  the  absolute  tem- 
peratures and 

P  X  1  PI  X  1 


492  560 

PI    —    1.14  P,  specific  pressure 
Pi    —    1.14  j>,  pounds  per  square  inch. 

GENERAL  EQUATION. — The  volume  occupied  by  a  pound  of 
air  at  any  given  pressure  and  temperature  (specific  volume) 
is  the  reciprocal  of  its  density  at  that  temperature.  At  32° 
F.  and  atmospheric  pressure  this  is  1  -f-  .0807  =  12.391.  Sub- 
stituting T,  =  (32  +  460),  P,  n  (14.7  X  144)  and  Vt  = 
12.391,  in  Equation  6  and  reducing 

PV   =    53.3   T  (7) 

This  is  usually  written  PV  =  727',  where  R  is  a  constant 
which  varies  for  different  gases.  In  further  study  of  this 
question,  it  is  found  that  7?  represents  the  foot  pounds  of 
external  work  done  when  the  temperature  of  one  pound  of 
gas  is  raised  one  degree  at  constant  pressure.  For  air,  as 
found  above,  it  is  53.3.  Having  the  value  7?  for  any  gas  and 
any  two  of  the  values  P,  V,  or  T,  the  third  may  be  found. 
Note:  in  Equation  7  P  and  V  must  be  specific  pressure  and 
volume,  respectively.  To  illustrate,  the  pressure  of  one 
pound  of  air  having  a  volume  of  5  cubic  feet  and  tempera- 
ture of  100°  F.  is  P  =  (53.3  X  560)  -r-  5  =  5969.6  pounds 
specific  pressure,  or  41.5  per  square  inch  absolute.  Also, 
the  volume  of  a  pound  of  air  having  a  pressure  of  50  pounds 
per  square  inch  absolute  and  a  temperature  of  60°  is  T  -. 
(53.3  X  530)  -r-  (64.7  X  144)  =  2.97  cubic  feet. 

10.  Combustion  of  Fuels: — Fuels  used  for  heat  produc- 
tion are  solid,  liquid  and  gaseous,  and  contain  carbon  (C), 
hydrogen  (77),  oxygen  (O),  nitrogen  (A7),  sulphur  (S),  and 
small  amounts  of  water  and  ash.  In  combustion  the  most 
valuable  of  all  of  these  constituents  are  carbon  and  hydro- 
gen. Fuels  with  high  percentages  of  carbon  and  hydrogen 
(heat  producing  agents)  and  low  percentages  of  ash  and 
water  are  the  most  desirable.  Coal  is  the  universal  fuel, 
although  oil  and  gas  are  frequently  used.  Carbon  burns  to 
carbon  dioxide  (CO2)  if  supplied  with  sufficient  air  during 
combustion  or  to  carbon  monoxide  (CO)  if  the  air  supply  is 
restricted.  The  greatest  economy  is  found  when  CO2  is 


COMBUSTION  OF   FUELS  27 

produced.  Hydrogen  burns,  forming  water,  and  sulphur 
burns  to  sulphur  dioxide  (SO2).  Oxygen  in  the  fuel  has  the 
same  effect  as  the  oxygen  of  the  air  in  supporting  combus- 
tion. Nitrogen  has  no  appreciable  chemical  action  during 
combustion,  but  it  absorbs  heat  and  is  thrown  away,  hence 
it  tends  to  reduce  the  efficiency  of  the  furnace.  Water  in 
the  fuel  has  little  chemical  effect.  It  absorbs  heat  in  being 
evaporated  and  superheated  and  passes  off  with  the  gases, 
causing  small  loss.  One  pound  each  of  the  above  elements 
of  the  coal  when  completely  consumed  gives  off  heat  units 
as  follows:  C  to  CO2  =  14600,  C  to  CO  =  4450,  CO  to  CO2  = 
10150,  //  to  H2O  —  62000  (frequently  used  52000  to  account 
for  loss  by  evaporation  and  superheating),  and  $  to  8O2  — 
4000. 

As  an  illustration  of  the  chemical  changes  taking  place 
in  a  furnace  when  a  fuel  is  raised  in  temperature  suffi- 
ciently high  that  the  combustible  unites  with  the  oxygen  of 
the  air  and  produces  combustion,  burn  completely  one  pound 
of  coal  containing  C  =  .78,  //  =  .04,  O  =  .03,  N  =  .02,  8  =  .02, 
H2O  =  .01,  and  ash  —  .10,  and  note  the  following  points  of 
interest: 

(A)  Theoretical  total  heat  of  the  fuel  by  equation. 

(B)  Amount  of  air  needed  for  complete  combustion. 

(a)    By  analysis,      (b)   By  equation. 
.     (C)      Probable  amount  of  air  used  for  combustion. 

(D)  Temperature  of  the  furnace  when  only  the  theoret- 

ical amount  of  air  is  used  for  complete  combus- 
tion. 

(E)  Temperature    of    the    furnace    when    the    probable 

amount  of  air  is  passed  through  the  furnace. 

(F)  Efficiency  of  the  furnace. 

THEORETICAL  TOTAL,  HEAT  OF  THE  FUEL  (A). — From  the  heat 
values  given  the  following  theoretical  equation  (Du  Long's 
formula)  has  been  compiled: 

O 

Total  Heat  =  14COO  C  +  52000  (//  -   — )  +  4000  8   (8) 

X 

and  when  applied  to  the  coal  sample  as  stated  gives 

.03 
Total   Heat    =    14600    X    .78    +    52000    X     (.04   -        — •)    + 

8 

4000  X  .02  =  13353  B.  t.  u.  Equation  8  is  used  when  the 
chemical  composition  of  the  fuel  is  known.  When  this  is  not 
known,  the  total  heat  is  found  in  the  laboratory  by  the  use 
of  calorimeters. 


28  HEATING  AND  VENTILATION 

In  most  furnfices  combustion  is  not  perfect.  Part  of  the  car- 
bon is  burned  to  CO2  giving-  off  14600  B.  t.  u.  per  pound  and 
part  to  CO  giving  off  4450  B.  t.  u.  per  pound.  To  find  the 
heat  value  of  the  coal  in  such  cases  use  a  modification  of 
Equation  8. 

Heat  liberated  =   14600  d  +  4450  Ca  -f   52000 
O 

(II  —  )    +   4000  8  (9) 

8 

where  C\  and  C»  =  weights  of  carbon  per  pound  of  coal 
burned  to  CO2  and  CO  respectively.  Suppose,  for  illustra- 
tion, that  the  carbon  goes  half  and  half  to  CO2  and  CO,  then 

the    heat   liberated    is    14600    X    .39    +    4450    X    .39    +    52000 

.03 
(.04 )    +    4000    X    .02    —    9395.     Compare   this  with   the 

O 

value  obtained  by  Equation  8. 

THEORETICAL  AMOUNT  OF  AIR  NEEDED  FOR  COMPLETE  COMBUS- 
TION (B). — 

(a)  Since  the  atomic  weights  (relative  weights  of  unit 
volumes  referred  to  H  =  1)  of  C  =  12,  H  =  1,  O  =  16,  N  —  14, 
and  8  =  32,  we  have 

12  parts  C  unite  with  32  parts  O.     (1  Ib.  C  +  2.66  Ibs.  O  — 

3.66  Ibs.  C02) 
12  parts  C  unite  with  16  parts  O.     (1  Ib.  C  -f  1.33  Ibs.  O  = 

2.33  Ibs.  (7) 
2  parts  H  unite  with  16  parts  O.     (1  Ib.  H  +  8.00  Ibs.  O  = 

9.00  Ibs.  H2O) 
32  parts  8  unite  with  32  parts  O.     (1  Ib.  8  +  1.00  Ibs.  O  = 

2.00  Ibs.  S02) 

from  which  may  be  found  the  oxygen  required  to  unite  with 
each  element  for  complete  combustion.  From  the  coal 
analysis, 

.78    X    2.66   =    2.075  Ibs.  O  for  the  ca.rbon 
.04    X    8.00    =      .320  Ibs.   0  for  the  hydrogen 
.02    X    1.00    =      .020  Ibs.  O  for  the  sulphur 

Total  2.415  Ibs.  O  per  Ib.  of  coal 

Less  .030  Ibs.  O  already  in  the  coal 

Net  total  =  2.385  Ibs.  O  per  Ib.  of  coal  to  be  taken 
from  the  air.  Atmospheric  air  contains  23  per  cent,  oxygen 
by  weight,  hence  it  will  require  2.385  -f-  .23  =  10.37  pounds 
of  air  to  completely  burn  the  pound  of  coal  if  all  the  oxygen 
of  the  air  is  used.  If  87  per  cent,  of  the  pound  of  coal  is 


COMBUSTION   OF   FUELS  29 

combustible,    then    there    are    needed    10.37     -H    .87    =    11.91 
pounds  of  air  per  pound  of  combustible. 

Where  combustion  is  not  perfect  the  theoretical  amount  of 
air  is  not  used.  Assume  as  before  that  the  carbon  divides 
half  and  half,  then  we  have 

For  Ci,  .39    X    2.66   =   1.036 

For  C2,  .39    X    1.33   =      .518 

For  H,    .04    X    8.00   =      .320 

For  8,    .02    X    1.00   =      .020 


Total  1.894  Ibs.  O 

Less  .030  Ibs.  O  in  coal 


Net  Total     1.864  Ibs.  O  to  be  taken  from 

the  air.  This  makes  1.864  -f-  .23  —  8.1  pounds  of  air  per 
pound  of  coal  burned.  Compare  this  value  with  that  for 
perfect  combustion. 

(b)  The  equation  usually  quoted  for  the  weight  of  air 
needed  for  perfect  combustion  is 

O 

W  -   11.52  C   +   34.56   (H )    +   4.32  8  (10) 

8 

which    for   the    assumed    coal    is   W    =    11.52    X    .78    +    34.56 
.03 

(.04 )   +  4.32   X   .02   =   10.32  pounds.     Compare  with  the 

8 
value  by  chemical  analysis. 

PROBABLE  AMOUNT  OF  AIR  USED  FOR  COMBUSTION  (C). — There 
can  be  no  exact  value  placed  tfpon  actual  amount  of  air  pass- 
ing through  a  furnace.  The  construction  of  the  furnace,  the 
type  of  grate  used,  the  depth  of  the  fuel  bed,  the  quality  of 
the  fuel  and  the  eccentricities  of  the  fireman  all  influence 
the  result.  From  tests  that  have  been  conducted  upon  vari- 
ous types  of  heating  furnaces  under  varying  conditions  of 
service,  it  seems  reasonable  to  assume  that  from  two  to 
three  times  as  much  air  goes  through  the  average  furnace  as 
would  be  needed  for  perfect  combustion.  In  the  most  up-to- 
date  power  plants  excess  air  is  reduced  to  small  amounts. 

It  is  not  possible  in  furnace  operation  to  keep  the  air 
supply  down  to  the  theoretical  amount  without  reducing  the 
economy  of  the  furnace.  When  the  fuel  bed  is  thick  and  the 
air  supply  reduced,  the  fuel  will  receive  too  small  an  amount 
of  air  and  carbon  will  be  burned  to  CO  with  a  loss  of  10150 
B.  t.  u.  per  pound.  When  the  fuel  bed  is  thin  and  the  supply 
of  air  excessive,  too  much  air  will  pass  through  the  fire 
causing  some  of  the  carbon  to  pass  off  unburned  and  carry- 


30  HEATING  AND   VENTILATION 

ing  away  heat  unnecessarily  by  heating  the  excess  air. 
(Read  Technical  Paper  No.  137,  Bureau  of  Mines,  Washing- 
ton, D.  C.)  Of  the  two  alternatives  it  is  better  to  have  too 
much  air  than  not  enough,  and  some  of  this  air  should  be 
admitted  above  the  fuel  bed.  To  illustrate  the  economy  of 
excess  air  in  practice,  suppose  the  pound  of  coal  just  con- 
sidered is  burned  in  a  furnace  where  the  entering  air  is  GO0 
and  the  stack  gases  are  600°.  With  the  specific  heat  of  the 
gases  =  .24  we  find  first,  for  perfect  combustion  with 
10.37  +  .9  =  11.27  pounds  of  stack  gases,  the  pound  of  coal 
has  available  for  boiler  use  (not  counting  radiation  losses) 
13353  —  [11.27  X  .24  X  (600  —  60)]  =  11892.4  B.  t.  u. 
Second,  if  there  is  just  enough  air  to  burn  the  carbon  to  CO, 
there  will  be  6.8  pounds  of  stack  gases  and  5436  —  [6.8  X 
.24  X  (600  r—  60)]  =  4555  B.  t.  u.  available.  Third,  with  2.5 
times  as  much  air  as  is  theoretically  needed  and  all  the  car- 
bon burned  to  CO2,  there  will  be  26.83  pounds  of  stack  gases 
per  pound  of  coal  and  the  heat  available  will  be  13353  - 
[26.83  X  .24  X  (600  —  60)]  =  9875.8  B.  t.  u.  This  shows  a 
decided  advantage  in  favor  of  excess  air  over  a  much  re- 
stricted supply.  Flue  gas  may  be  analyzed  by  the  Orsat  ap- 
paratus and  such  analysis  used  in  determining  the  quality 
of  the  combustion  (See  Art.  17). 

THEORETICAL  TEMPERATURE  OF  THE  FURNACE  (D). — When  per- 
fect combustion  occurs,  the  theoretical  total  heat  is  given 
off.  If  it  were  possible  to  liberate  this  heat  in  a  vessel  per- 
fectly insulated,  all  the  liberated  heat  would  be  used  in  rais- 
ing the  temperature  of  the  gases.  The  theoretical  rise  in 
temperature  in  such  an  ideal  furnace  would  be 

theoretical  total  heat   (B.  t.  u.) 

tr   =   (11) 

pounds  of  stack  gases  X  specific  heat 

Applying  to  the  coal  sample  above,  tr  —  13353  -f-  (11.27  X 
.24)  =  4946°  F.,  and  if  the  air  enters  at  60°,  the  temperature 
of  the  furnace  is  4946  +  60  =  5006°  F. 

PROBABLE  TEMPERATURE  OF  THE  FURNACE  (E). — Suppose  2.5 
times  the  theoretical  air  is  used  in  the  furnace,  then  the 
probable  temperature  is 

13353 

t  — [.  60  =   2138°  F. 

26.83    X    .24 

Radiation  and  other  losses  will  reduce  this  value  somewhat. 

EFFICIENCY    IN    FURNACE    COMBUSTION    (F). — There    are    five 

losses  in  fuel  combustion:  (a)  unburned  combustible  material 

that   drops   through    the   grate   with    the   ash,    (b)    unburned 


COMBUSTION  OF   FUELS  31 

hydrocarbon  particles  that  leave  the  chimney  as  smoke,  (c) 
carbon  burned  to  CO  instead  of  CO2  by  incomplete  combus- 
tion, (d)  excessive  air  supply,  (e)  radiation.  These  losses 
are  apportioned  about  as  follows: 

(a)  (Estimated)  1  to  3  per  cent,  of  total  heat  in  coal. 

(b)  (Estimated)   1  to  5  per  cent,  of  total  heat  in  coal. 

(c)  May  vary  anywhere  between  10  and  50  per  cent. 

(d)  May  vary  anywhere  between     5  and  15  per  cent. 

(e)  (Estimated)  2  to  5  per  cent. 

It  will  be  seen  by  this  that  a  large  part  of  the  original  heat 
in  the  coal  is  not  transferred  through  the  heating  surface 
of  the  boiler  to  the  water,  but  is  dissipated  through  the  five 
channels  just  mentioned. 

Intimately  associated  with  the  combustion  losses  is  the 
idea  of  furnace  and  Idler  efficiencies.  The  most  important  of 
these  are  grate  efficiency,  furnace  efficiency  and  overall 
efficiency. 


Grate  efficiency  = 

weight  (or  heat  value)  of  ascending  combustible 


weight  (or  heat  value)  of  combustible  fired 


(12) 


If   2   per  cent,   of   the  coal   drops   through   the   grate,   this   is 
(100  —  2)   -=-  100  =  98  per  cent. 
Furnace  efficiency   = 

heat  available  for  absorption  by  boiler 

(13) 


heat  value  of  combustible  fired 

With  perfect  combustion  of  the  entire  pound  of  coal  and  2.5 
times  the  required  amount  of  air,  this  is  9875.8  -7-  13353  —  74 
per  cent.  If  there  is  a  percentage  loss  through  the  grate, 
the  value  9875.8  will  be  reduced  by  this  amount.  With  im- 
perfect combustion,  illustrated  by  the  case  where  the  carbon 
divides  half  and  half  to  CO2  and  CO,  this  is  [9395  —  9  X  .24 
(600  —  60)]  -r-  13353  =  61  per  cent.  If  there  is  a  percentage 
loss  through  the  grate,  the  value  9395  will  be  reduced  by 
this  amount. 

heat  absorbed  by  water  and  steam 

Over-all  efficiency  =  —  —   (14) 

heat  value  of  combustible  fired 

The  heat  absorbed  by  the  water  and  steam  is  the  heat  value 


32  HEATING  AND  VENTILATION 

of  the  combustible  less  all  the  losses.  Suppose  the  losses  in 
the  sample  are: 

through  the  grate,  .02    X    13353    =      267.06  B.  t.  u.; 

unburned  carbon  (smoke),  .03    X    13353    =      400.59  B.  t.  u. 

imperfect  combustion,  .20    X    13353    =    2670.60  B.  t.  u. 

excessive  air  supply,  .10    X    13353    =•  1335.30  B.  t.  u. 

radiation,  .02    X    13353    =      267.06  B.  t.  u. 

total  losses,  4940.61  B.  t.  u. 

then  the  over-all  efficiency  is  (13353  —  4940.61)  -4-  13353  = 
63  per  cent.  When  the  word  efficiency  is  mentioned  in  con- 
nection with  small  power  and  heating  plants,  the  over-all 
efficiency  is  understood  unless  otherwise  specified.  The  effi- 
ciency of  the  average  boiler  is  60  to  65  per  cent.,  but  efficien- 
cies as  high  as  75  per  cent,  may  be  found  in  continuous 
service  in  some  of  the  better  plants  (For  boiler  operation, 
see  Arts.  87  and  187). 

17.  Flue  Gas  Analysis. — The  quality  of  the  fuel  combus- 
tion in  many  plants. is  determined  by  the  Orsat,  or  similar 
apparatus,  which  is  used  in  obtaining  an  analysis  of  the  flue 
gases  by  volume  as  they  leave  the  boiler.  Values  are  found 
for  CO2,  CO  and  O.  The  CO2  varies  from  6  to  17  per  cent,  of 
the  total  volume  of  the  flue  gases.  Between  10  and  13  per 
cent,  is  considered  good  practice.  CO  is  always  found  in 
small  quantities,  say  from  0  to  .5  per  cent.  When  excess  air 
is  less  than  25  per  cent.,  CO  is  probably  forming  in  prohibi- 
tive amounts.  With  good  combustion  and  100  per  cent,  excess 
air  (good  boiler  practice),  there  should  be  but  a  trace  of  CO. 
Free  oxygen  is  always  found  where  there  is  an  excess  of 
air.  This  percentage  of  O  (0  to  15  per  cent.)  may  be  used  to 
determine  the  amount  of  excess  air. 

Of  the  three  determinations  made  by  the  use  of  the 
Orsat  apparatus,  the  CO»  and  O  determinations  are  consid- 
ered of  greatest  value.  When  carbon  and  oxygen  unite  to 
form  carbon  dioxide  gas,  it  is  found  that  with  the  same  tem- 
perature and  pressure  the  carbon  dioxide  occupies  the  same  volume 
as  the  oxygen  entering  into  the  combination.  Assuming  perfect 
combustion  (no  carbon  monoxide)  and  just  enough  air  to 
supply  the  oxygen,  the  resulting  gas  volumes  will  be  21  per 
cent.  CO2  and  79  per  cent.  N.  A  test  with  the  Orsat  in  this 
case  should  show  21  per  cent.  C02,  0  per  cent.  CO,  and  0  per 
cent.  O.  Again,  assuming  perfect  combustion  and  an  excess 
of  air  (say  100  per  cent.),  one-half  of  the  oxygen  of  the  air 
is  used  for  the  CO2  and  the  Orsat  should  show  10.5  per  cent. 


FLUE   GAS  ANALYSIS  33 

CO2,  10.5  per  cent.  O,  and  0  per  cent.  CO.  That  is  to  say,  the 
sum  of  the  CO2  and  O  percentages  will  be  21  per  cent.,  the  same 
as  the  original  oxygen  volume.  Again,  assuming  imperfect 
combustion  and  a  certain  amount  of  CO,  it  is  found  that 
ivith  the  same  temperature  and  pressure  the  carbon  monoxide  occu- 
pies twice  the  volume  of  the  oxygen  entering  into  the  combination 
and  the  resulting  stack  gases  have  a  larger  volume  than  the 
entering  air  by  one-half  of  the  percentage  of  CO  present. 
With  high  percentages  of  CO  this  change  in  volume  would 
need  to  be  taken  into  account.  In  all  ordinary  cases,  how- 
ever, it  is  satisfactory  to  consider  the  stack  gases  as  79  per 
cent.  N  and  the  remaining  21  per  cent,  composed  of  CO2,  CO 
and  O.  21  per  cent.  CO2  shows  the  highest  possible  efficiency, 
i.  e.,  no  excess  air  and  perfect  combustion.  This  is  never 
obtained  in  practice.  Any  value  of  CO.,  less  than  this  indi- 
cates (1)  excess  of  air,  if  no  CO  is  present;  (2)  deficiency  of 
air,  if  CO  is  present  and  no  O;  (3)  improper  mixture  in  the 
combustion  chamber,  if  both  CO  and  O  are  present. 

Computations  to  find  the  relation  between  weights  of  flue  gas 
and  entering  air  are  sometimes  complicated  by  the  necessity 
of  changing  from  weights  to  volumes  and  vice  versa.  Vol- 
ume readings  of  the  Orsat  are  generally  used  directly  in 
terins  of  the  densities  of  the  gases  since,  as  above  stated, 
equal  volumes  of  the  gases  at  the  same  temperature  and 
pressure  contain  the  same  number  of  molecules.  Use  the 
equations  44  COn  +  32  Oo  +  28  (CO  +  N) 

W  =  -  -  X   Cl  (15) 

12   (CO.,   +   CO) 

Where  W  —  weight  of  flue  gas  in  pounds  per  pound  of  coal, 
Ci  —  percentage  of  carbon  in  the  coal,  and  the  other  symbols 
represent  percentages  of  each  as  shown  by  the  Orsat.  2V  is 
found  by  differences  i.  e.,  100  —  (CO2  +  CO  +  O).  For  infor- 
mation on  the  use  of  the  Orsat  apparatus  see  very  excellent 
explanation  in  ''Coal,"  by  Somermcicr. 

APPLICATION  (1). — Coal,  having"  a  composition  as  stated 
in  Art.  16,  is  being  burned  in  a  furnace  without  loss  through 
the  grate.  Samples  of  the  flue  gas  show  12  per  cent.  CO2 
and  9  per  cent.  O.  What  is  the  weight  of  flue  gases  per 
pound  of  coal  burned?  Compare  this  value  with  the  the- 
oretical amount  of  air  as  in  Art.  16  (B)  and  note  the  excess 
supplied.  From  Equation  15 

44    X    12   +   32    X    9   +   28    X    79 

W  =  -   X    .78   =   16.4 

12   (12   +   0) 


34  HEATING  AND  VENTILATION 

Excess  air  =  16.4  —  10.37  =  6.03  pounds.  Where  a  grate 
loss  js  known  to  exist,  C^  should  be  corrected  by  this 
amount.  Thus  for  a  2  per  cent,  loss,  d  =  .98  X  .78  —  .764. 
APPLICATION  (2). — Coal  as  in  application  (1);  2  per  cent, 
loss  through  the  grate;  8  per  cent.  CO2;  12.5  per  cent.  O;  .5  per 
cent.  CO.  Find  the  weight  of  stack  gases  and  excess  air  per 
pound  of  coal. 

44    X    8   +   32    X    12.5    +    28   (.5    +   79) 

W  =  -   X    .764   =   22.3 

12   (8  +  .5) 

Excess  air  —   22.3  —  10.37  —  11.93. 


-f9C{    HI    v 
aiffl    ^<j    N 
(Mi// 


CHAPTER  II. 


AIR    COMPOSITION — VENTILATION — HUMIDITY — DRAFT. 


18.  Composition  of  Atmospheric  Air: — The  subject  of 
ventilation  in  its  relation  to  health  should  be  introduced  by 
a  brief  consideration  of  the  properties  of  the  air  supplied. 
Air  is  a  very  important  factor  in  building"  economy.  In  addi- 
tion to  its  value  as  a  heating  medium  it  determines  in  a 
marked  degree  the  health  of  the  occupants  of  the  building1. 

The  human  body  may  be  considered  a  well  equipped  and 
very  complex  power  plant.  As  the  carbon,  hydrogen,  and 
oxygen  in  the  fuel  and  air  supply  in  any  mechanical  power 
plant  are  consumed  in  the  furnace,  the  resulting  heat  ab- 
sorbed in  the  generating  system  and  finally  turned  into 
work  through  the  attached  mechanisms;  so  the  human  body 
absorbs  heat  from  the  combustion  of  food  and  turns  it  into 
work.  The  products  of  combustion  in  both  cases  are  largely 
carbon  dioxide  and  water.  The  chief  requisites  of  the 
mechanical  plant  are  good  fuel,  well  regulated  draft  and 
efficient  stoking.  Similarly,  the  human  body  needs  good 
food,  pure  air  and  healthful  exercise.  Of  the  three  require- 
ments all  are  of  the  utmost  importance,  but  the  second  has 
probably  the  greatest  significance,  since  no  person  can  long 
keep  in  health  with  impure  air,  even  with  the  best  of  food 
and  a  sufficient  amount  of  exercise. 

In  its  simplest  analysis  air  is  made  up  of  two  elements, 
oxygen  and  nitrogen,  in  the  volume  ratio  of  20.9  to  79.1  and 
a  density  ratio  of  23.1  to  76.9,  respectively.  In  a  complete 
analysis  of  pure  air  a  number  of  other  elements  and  com- 
pounds are  found,  making  a  mechanical  mixture  that  is 
somewhat  complex.  Most  air  samples  show  traces  of  carbon 
monoxide,  hydrogen  sulphide,  ozone,  argon,  compounds  of 
ammonia,  and  compounds  of  nitric,  nitrous,  sulphuric  and 
sulphurous  acids.  The  heating  and  ventilating  engineer, 
however,  is  interested  chiefly  in  the  amount  of  oxygen, 
moisture  and  carbon  dioxide  present.  Air  taken  from  the 
open  country  and  not  contaminated  with  the  poisonous  gases 
or  the  dus+  and  refuse  from  cities  has  the  following  com- 


36  HEATING   AND   VENTILATION 

position  according-  to  Professor  Carpenter.  Heating  and 
Ventilating  Buildings  (See  also  Encyclopedia  Britannica, 
Respiration). 

Oxygen  Per  cent,  of  volume   20.26 

Nitrogen  "  "          "  78.00 

Moisture  1.70 

Carbon  dioxide  "          "  .04 

These  values  are  fairly  constant,  except  that  of  the  moisture 

which  may  vary  from  0+  to  4  per  cent,  of  the  entire  weight 

of  the  air. 

Experiments  have  shown  that  normally  pure  air  in  the 
process  of  respiration  when  exhaled  from  the  lungs  of  the 
average  person  has 

Oxygen  Per  cent,  of  volume   16 

Nitrogen  75 

Moisture  5 

Carbon  dioxide  4 

Comparing  these  values  with  those  for  pure  air,  oxygen  is 
reduced  one-fifth,  nitrogen  is  reduced  one  twenty-fifth,  vapor 
is  increased  three  times  and  carbon  dioxide  is  increased  one 
hundred  times.  Oxygen  has  been  consumed  in  its  union  with 
the  excess  carbon  and  hydrogen  in  the  human  body  and  is 
given  off  as  carbon  dioxide  and  water  vapor.  It  may  be 
seen  from  these  ratios,  that  the  gradual  reduction  of  the 
oxygen  content  and  the  very  rapid  increase  of  CO2  with  its 
accompanying  impurities  soon  render  unfit  for  use  the  air 
in  any  building  occupied  by  a  number  of  people.  To  avoid 
this  state  of  affairs,  fresh  air  should  be  supplied  continu- 
ously and  at  such  points  as  will  provide  the  most  uniform" 
circulation. 

19.  Oxygen  and  Nitrogen: — Oxygen  fills  about  one-fifth 
of  the   volume   in   atmospheric   air   and   is   the   element   that 
makes    combustion    possible.      The    other    four-fifths    of    the 
space    is    filled    with    nitrogen.      In   a   providential    way    this 
nitrogen  acts  with  the  oxygen  to  control  the  rapidity  with 
which  combustion  takes  place.     Nitrogen  seems  to  have  little 
effect  upon  respiration,  except  to  retard  chemical  action.     If 
one  were  to  attempt  to  live  in  an  atmosphere  of  pure  oxy- 
gen,   the    chemical    action    taking    place    through    the    lungs 
would  be  so  rapid  that  the  human  body  would  not  be  able 
to  maintain  it. 

20.  Carbon  Dioxide: — The   amount   of   CO2    in   the   air   is 
used  as  an  index  to  the  purity  of  the  air.     It  is  not  consid- 


COMPOSITION   OP   AIR  37 

ered  a  poisonous  gas.  It  has  slight  taste  and  odor,  but  no 
color.  It  is  found  in  many  natural  waters  and  manufac- 
tured beverages,  the  chief  one  being  "soda  water,"  which  is 
made  by  forcing  carbon  dioxide  into  water  under  pressure. 
The  real  action  of  CO2  when  taken  into  the  lungs  is  not  well 
"known.  It  has  the  effect  of  producing  physical  depression 
and  where  found  in  sufficient  quantity  will  even  cause  death 
by  suffocation,  very  similar  to  submergence  in  water.  What- 
ever its  effect  upon  human  life  may  be,  its  presence  in  any 
room  used  for  habitation  (assuming  no  open  fires  or  gas  jets 
in  the  room)  is  an  indication  of  the  lack  of  oxygen  and  an 
excess  of  impurities  thrown  off  by  respiration.  Good  coun- 
try air  has  4  parts  CO2  in  10000  parts  of  air  and  room  air 
should  never  be  allowed  to  have  more  than  8  to  10  parts  in 
10000  parts  of  air.  It  becomes  the  duty  of  the  heating  engi- 
neer therefore  to  provide  pure  air  in  sufficient  quantities,  to 
enter  and  withdraw  the  air  from  the  room  in  a  manner  such 
as  will  not  be  uncomfortable  to  the  occupants  and  to  keep 
the  air  fairly  uniform  in  quality  throughout  the  room.  Car- 
bon dioxide  is  52  per  cent,  heavier  than  air  of  the  same  tem- 
perature and  therefore  has  a  tendency  to  fall.  Exhaled  air, 
however,  has  excessive  moisture,  has  a  temperature  much 
higher  than  that  of  the  room  air  and  is  2  to  3  per  cent, 
lighter  than  when  inhaled.  Its  tendency  to  rise  neutralizes 
the  excessive  density  of  the  CO2  and  as  long  as  the  air  is 
absolutely  quiet,  results  in  a  fair  diffusion  throughout  the 
room  air.  In  large  audience  rooms  the  heat  given  off  from 
the  occupants  is  sufficient  to  cause  strong  currents  which 
carry  this  impure  air  to  the  upper  part  of  the  room.  A  care- 
ful study  of  the  physical  conditions  within  inhabited  rooms 
shows  that  the  location  of  the  b<i<l  air  zone  may  be  anywhere 
from  the  floor  to  the  ceiling,  depending  upon  the  room  vol- 
ume (large  or  small  respectively)  allowed  per  inhabitant 
and  the  rapidity  of  air  movement  in  the  room.  In  investi- 
gating air  conditions,  tests  for  C02  should  be  made  in  all 
sections  of  the  room.  Tests  conducted  at  the  breathing  line 
represent  living  conditions  for  the  inhabitants.  In  residence 
work  air  is  usually  entered  and  withdrawn  at  the  floor  line. 
In  large  plants  where  the  air  circulates  by  mechanical 
means,  it  usually  enters  above  the  heads  of  the  occupants 
and  is  withdrawn  at  the  floor  line.  Some  engineers  advo- 
cate the  updraft  system  with  the  air  entering  near  the  floor 
and  leaving  at  the  ceiling.  In  the  latter  case  ventilation  is 
simplified  but  heating  is  made  very  expensive. 


38 


HEATING  AND  VENTILATION 


A  method  of  determining  the  percentage  of  carbon  dioxide  in 
the  air,  based  upon  the  fact  that  barium  carbonate  is  nearly 
insoluble  in  water,  may  be  performed  as  follows:  provide 
eleven  bottles  with  rubber  stoppers  having-  two  holes  each 
and  connect  them  continuously  by  glass  and  rubber  tubing, 
so  that  if  suction  be  applied  at  the  first  bottle  of  the  series 
air  will  be  drawn  in  at  the  last  of  the  series  and  the  same 
air  will  be  passed  through  all.  In  this  way  a  sample  of  the 
air  to  be  tested  may  be  drawn  into  each  bottle.  The  capac- 
ities of  the  bottles  in  ounces  must  be  respectively,  23^,  18 %. 
16%,  14,  9^,  1V2,  5%,  4,  31/4,  2%  and  2.  These  may  readily 
be  prepared  by  partially  filling  with  paraffin.  Into  each 
bottle  is  then  placed  %  ounce  of  a  50  per  cent,  saturated 
solution  of  barium  hydrate  (Ba(OH)2).  Air  to  be  tested 
is  drawn  through  the  system  until  all  the  bottles  contain  a 
fair  sample.  Each  bottle  is  then  thoroughly  shaken,  so  that 
the  liquid  may  be  brought  into  good  contact  with  the  air 
sample.  If  the  least  turbidity  or  cloudiness  appears  it  indi- 
cates 

First  or  largest  bottle,  0.04  per  cent.  C02 


Second  bottle, 

Third 

Fourth      " 

Fifth 

Sixth 

Seventh    " 

Eighth      " 

Ninth 

Tenth 

Eleventh  " 


0.06 
0.07 
0.08 
0.10 
0.15 
0.20 
0.30 
0.40 
0.60 
0.90 


The  g-lass  tubes  should   extend  no  farther  than  the  bottom 
of   the   stoppers.      Fig.    4,   a,    shows   four   of   the   bottles   and 


(a) 


Fig".  4. 


COMPOSITION  OF  AIR  39 

their  connections.  To  illustrate,  suppose  that  the  air  of  a 
room  was  tested  and  that  in  the  first,  second,  third,  fourth, 
fifth  and  sixth  bottles  the  liquid  became  turbid  after  vigor- 
ous shaking.  Such  room  air  would  have  contained  0.15  per 
cent,  carbon  dioxide  and  would  have  been  considered  quite 
unfit  for  breathing. 

A  second,  less  cumbersome  method  of  testing  for  the  per- 
centage of  carbon  dioxide  is  shown  in  Fig.  4,  6.  A  bottle  of 
about  6  ounces  capacity  is  fitted  with  a  rubber  stopper  hav- 
ing two  holes.  Through  one  hole  a  glass  tube  is  brought 
from  the  bottom  of  the  bottle  and  to  the  outer  end  of  this 
tube  is  connected  a  valved  bulb  similar  to  those  found  on 
atomizers.  Into  the  bottle  are  placed  10  cubic  centimeters 
of  a  solution  made  by  dissolving  .53  gram  of  anhydrous 
sodium  carbonate  (Na2CO3)  in  5  liters  of  water  and  adding 
.01  gram  of  phenolphthalein.  The  water  used  must  have 
been  previously  boiled  for  at  least  one  hour  in  an  open  ves- 
sel. With  the  apparatus  so  prepared,  squeeze  the  bulb,  thus 
forcing  air  from  the  room  through  the  liquid  and  into  the 
bottle.  The  open  hole  in  the  rubber  stopper  is  then  closed 
with  the  thumb  and  the  bottle  vigorously  shaken.  Then 
another  bulb  full  of  air  is  injected  and  the  bottle  again 
shaken.  This  process  is  continued  and  the  number  of  bulbs 
of  air  noted  until  the  red  color  of  the  solution,  due  to  the 
phenolphthalein,  disappears.  This  number  of  bulb  fillings 
when  referred  to  a  table  (Similar  to  Table  II)  prepared  for 
this  particular  apparatus,  is  indicative  of  the  purity  of  the 
air.  After  such  an  apparatus  is  completed  it  must  be  cali- 
brated before  being  used.  This  is  done  by  obtaining  the 
number  of  bulb  fillings  of  pure  country  air  necessary  to  clear 
the  liquid,  which  will  usually  vary  from  40  to  70.  The  table 
for  use  with  this  special  apparatus  may  be  obtained  by  pro- 
portion from  Table  II,  in  which  the  number  of  bulb  fillings 
of  country  air  is  48.  If  now  with  the  new  apparatus  it  is 
found  that  60  bulb  fillings  are  required  to  clear  the  liquid, 
the  proportionate  table  would  be  made  by  multiplying  the 
number  of  bulb  fillings  given  below  by  the  ratio  of  60  -r-  48, 
or  5  to  4.  It  is  important  that  the  bulb  be  compressed  the 
same  amount  for  each  filling,  and  that  the  shaking  of  the 
bottle  and  contents  be  continued  the  same  length  of  time 
after  each  filling,  to  obtain  uniform  results.  The  Wolpert 
Air  Tester,  a  commercial  apparatus,  may  be  obtained  for 
this  line  of  testing. 


4U  HEATING  AND   VENTILATION 

TABLE  II. 


Fillings 

Per  cent.  CO2 

Fillings 

Per  cent.  CO2 

48 

.030 

15 

.074 

40 

.038 

14 

.077 

35 

.042 

13 

.080 

30 

.048 

12 

.083 

28 

.049 

11 

.087 

IM; 

.051 

10 

.090 

24 

.054 

9 

.100 

22 

.058 

8 

.115 

20 

.062 

7 

.135 

19 

.064 

6 

,155 

18 

.066 

5 

.180 

17 

.069 

4 

.210 

16 

.071 

3 

.250 

The  methods  just  mentioned  for  determining-  CO2  are 
fairly  satisfactory  in  obtaining-  quantitative  values  from 
which  the  quality  of  the  ventilating  air  in  any  system  may 
be  judged.  If  exact  percentages  of  CO,  CO.,,  O  and  N  are  re- 
quired, the  Pettersson-Palmquist,  the  Orsat,  or  similar  ap- 
paratus must  be  employed.  For  descriptions  of  these  see 
Stillmans'  Engineering  Chemistry,  Carpenter's  Heating  and 
Ventilating  Buildings,  Hempel's  Gas  Analysis,  translated  by 
Dennis,  Abady's  Gas  Analyst's  Manual,  and  Somermeier's 
Coal. 

21.  Amount  of  Fresh  Air  Needed  per  Person: — The  need 
of  a  continuous  supply  of  fresh  air  in  residences  and  busi- 
ness houses  can  scarcely  be  overestimated.  Health  is  the 
greatest  of  all  blessings  and  ]>iirc  air  is  essential  to  health.  The 
most  convincing  argument  that  can  be  presented  on  this 
point  is  an  analysis  of  the  vital  statistics  of  the  country 
covering  a  large  number  of  years.  Persons  afflicted  with 
respiratory  diseases  are  recommended  by  the  medical  fra- 
ternity to  seek  a  high,  dry,  sunny  climate,  and  lire  in  the 
open  air.  The  rarefied  atmosphere  causes  continuous  deep 
breathing,  which  exercise  in  itself  has  a  tendency  toward 
strengthening  the  afflicted  parts  and  throwing  off  disease, 
and  the  dry  air  probably  serves  the  lung  tissue  as  a  cleanser 
as  the  blotter  does  the  page  of  wet  ink.  These  condi- 
tions, in  connection  with  the  sunshine  which  is  one  of  our 


AIR   REQUIRED   PER   PERSON  41 

best  germicides,  form  the  only  known  remedy  for  combating 
such  diseases.  It  is  a  safe  conclusion  that  the  element  of 
pure  air  which  enters  so  largely  into  the  overcoming  of  the 
disease,  once  it  is  contracted,  is  one  of  the  best  preventives 
as  well.  Statements  are  made  (occasionally  in  the  technical 
press)  that  respired  air  is  not  harmful  and  that  satisfactory 
ventilation  may  be  had  in  inhabited  rooms  with  much  less 
fresh  air  than  that  usually  allowed.  The  first  of  these  two 
statements  has  never  been  proved.  On  the  contrary  the  cir- 
cumstantial evidence  of  the  impurity  of  respired  air  is  fairly 
conclusive.  The  second  may  be  true  for  ventilating  systems 
where  the  air  supply  is  subdivided  into  small  amounts  and 
carried  directly  to  the  person  (See  experiments  by  Professor 
Bass  at  University  of  Minnesota,  Trans.  A.  S.  H.  &  V.  E., 
Vol.  XIX,  p.  328).  Applications  such  as  this,  however,  can 
not  be  regarded  as  touching  general  practice. 

The  average  adult,  when  engaged  in  ordinary  indoor 
occupations,  will  exhale  about  20  cubic  inches  of  air  per 
respiration.  He  will  also  have  16  to  24  respirations  per 
minute,  totaling  400  -f-  cubic  inches  or,  say  .25  cubic  foot  of 
air  per  minute.  Allowing"  4  per  cent.  C'O2  in  respired  air  the 
average  person  will  exhale  60  X  .25  X  .04  =  .6  cubic  foot 
CO2  per  hour.  This  is  constantly  being  diffused  throughout 
the  air  of  the  room.  If  the  carbon  dioxide  and  other  impur- 
ities could  be  disassociated  from  the  rest  of  the  air  and  ex- 
pelled from  the  room  without  taking  large  quantities  of 
otherwise  pure  air  with  them,  the  problems  of  the  heating 
and  ventilating  engineer  would  be  simplified,  but  this  cannot 
be  done.  Rapid  diffusion  of  respired  air  throughout  the  room 
renders  it  necessary  to  dilute  the  room  air  with  fresh  air  in 
order  that  the  purity  may  be  maintained  at  a  safe  value. 
Ideal  conditions  are  found  when  interior  air  is  as  pure  and 
refreshing  as  that  of  the  open  country,  but  the  mechanical 
difficulties  around  such  a  ventilating  system  would  be  so 
great  as  to  render  it  prohibitive.  The  standard  of  purity 
which  should  be  aimed  at,  and  which  may  be  obtained  with 
a  first-class  system,  is  .06  of  one  per  cent.  CO.2,  i.  e.,  6  parts 
of  CO2  in  10000  parts  of  air.  Systems  maintaining  constant 
ventilation  at  8  parts  in  10000  are  considered  satisfactory. 
Stated  in  a  simple  form  for  calculation,  let  Q'  =  cubic  feet 
of  atmospheric  air  needed  per  hour  per  person,  A  •=  cubic 
feet  of  C02  given  off  per  hour  per  person,  n  —  standard  of 
purity  to  be  maintained  (allowable  parts  of  CO2  in  10000 


42  HEATING  AND  VENTILATION 

parts   of  air),   and  p    =    standard   of  purity   in   atmospheric 

air,  say  4;  then 

A 

Q'  =  (16) 

n  —  p 

To  maintain  constant  ventilation  at  7  parts  C02  in  10000 
parts  of  air,  with  pure  air  at  4  parts  in  10000,  we  have  Q'  = 
.6  -f-  (.0007  —  .0004)  =  2000  cubic  feet  of  air  per  hour.  Based 
upon  .6  cubic  foot  of  CO2  exhaled  per  person  per  hour,  Table 
III  gives  the  amount  of  air  needed  to  maintain  constant  ven- 
tilation at  the  various  standards  of  purity. 

TABLE  III. 
Cubic  Feet  of  Air  per  Person  per  Hour. 


n 

A 

Q 

6 

.6 

3000 

7 

.6 

2000 

8 

.6 

1500 

9 

.6 

1200 

10 

.6 

1000 

It  should  be  understood  that  no  hard  and  fast  rule  can 
be  given  for  the  air  requirement  per  person.  This  varies 
with  the  physical  development  and  occupation  of  the  indi- 
vidual, but  it  varies  in  a  greater  degree  with  the  state  of 
the  person's  health  and  the  sanitary  value  of  his  surround- 
ings. In  general,  the  average  adult  subjected  to  average  in- 
door conditions  requires  1800  cubic  feet  of  fresh  outdoor  air  per 
hour.  Stated  as  an  equation,  the  amount  of  air  needed  for 
ventilation  is  Q'  =  1800  N,  where  N  =  the  number  of  people 
to  be  provided  for. 

The  amounts  of  air  in  cubic  feet  per  person  per  hour 
given  in  Table  IV,  may  be  considered  good  practice  for  the 
various  classes  of  service. 

TABLE   IV. 


Hospitals,  Ordinary 

Surgery 

Epidemic 
Workshops,  Ordinary 

"  Unhealthy  trades 

Schools,  Offices,  Prisons 
Theaters  and  Assembly  Halls 


2000-2500 

2500-3000 

5000-6000 

1800-2000 

3000-3500 

1800 

1400-1800 


VENTILATION  43 

One  ordinary  gas  flame  of  16  to  20  candle  power,  using 
4  to  5  cubic  feet  of  gas  per  hour,  will  vitiate  as  much  air  as 
four  or  five  people.  Where  many  open  flame  gas  lamps  are 
used,  this  fact  should  be  taken  into  account. 

22.  Ventilation: — Ventilation  is  the  art  of  maintaining  in- 
terior atmospheres  at  a  comfortable  temperature  and  humidity,  and 
a  purity  approaching  that  of  open  country  air.  Such  a  standard 
may  be  regarded  absolutely  safe  by  any  one.  To  accomplish 
this,  large  amounts  of  fresh  air  should  be  introduced  to  the 
building  and  distributed  so  the  occupants  will  not  be  sub- 
jected to  unpleasant  drafts.  Fans  placed  in  the  rooms  to 
circulate  the  air  make  the  room  atmosphere  more  habitable 
on  a  warm  day,  but  this  process  should  not  be  mistaken  for 
ventilation.  The  mere  process  of  fanning  the  air  does  not  purify  it. 
Air  may  be  tested  for  bacteria  and  micro-organisms  by 
exposing  specially  prepared  gelatine  plates  or  tubes  to  the 
air  of  a  room  a  certain  length  of  time,  say  five  or  ten  min- 
utes, permitting  the  organisms  to  germinate  and  counting 
the  colonies.  (See  Report  of  Ventilation  Division,  Chicago 
Health  Dept.,  Page  57,  Vol.  XX.  Trans.  A.  S.  H.  &  V.  E.) 
Such  tests  are  most  satisfactory  but  require  considerable 
care  in  application  and  are  not  generally  used.  The  CO2 
test  mentioned  in  Art.  20,  while  not  a  direct  equivalent,  is 
simpler  and  is  generally  employed.  In  testing  the  quality 
of  room  air  by  any  method  it  is  well  to  call  attention  to  the 
fact  that  the  ordinary  running  conditions  of  any  room  can- 
not absolutely  be  determined  by  a  single  test.  Trials  should 
frequently  be  made  and  records  kept.  Upon  one  day  atmos- 
pheric conditions  may  be  favorable  and  tests  may  show  a 
small  amount  of  impurity.  On  other  days  when  the  condi- 
tions are  not  as  favorable  impurities  may  be  found  in  large 
quantities  even  though  running  conditions  seem  to  be  dupli- 
cated. Further,  if  the  only  requirement  governing  the  ven- 
tilation of  buildings  is  that  a  satisfactory  <7O2  test  be 
passed,  there  is  great  danger  of  overrating  or  underrating 
the  ventilating  system  of  the  building.  A  safe  method  in  rat- 
ing ventilating  systems  is  to  require  a  minimum  air  supply  in  addi- 
tion to  a  maximum  permissible  percentage  of  CO%  at  the  breathing 
line.  For  further  study  of  this  subject,  see  recommendations 
by  the  American  Society  of  Heating  and  Ventilating  Engi- 
neers, Jour.  Apr.  1916,  p.  91.  Also  Trans.  A.  S.  H.  &  V.  E.. 
Vol.  XXII,  p.  43. 

23.     Air   Purification: — Air   contains   dust,   fine   particles 
of  mineral  and  animal  matter,  bacteria,  and  micro-organisms 


44  HEATING  AND  VENTILATION 

held  in  mechanical  suspension.  The  more  heavily  charged 
with  these  impurities  ventilating  air  becomes,  the  more  dan- 
gerous it  is  to  the  human  system.  Most  materials  held  in 
mechanical  suspension  may  be  removed  by  filtering  (passing- 
through  fine  cloth  screens)  or  by  irunliiin/  (passing  through 
films  or  sprays  of  water).  Filtering  and  washing  systems 
are  beneficial  in  all  cases  and  are  necessities  in  many.  Fil- 
ters cost  less  to  install  and  operate,  but  they  occupy  larger 
transverse  areas  and  are  not  as  effective  as  the  washing 
systems.  Washing  air  removes  most  of  the  mechanically 
suspended  particles  but  it  does  not  necessarily  eliminate 
chemical  impurities,  bacteria  and  the  like.  The  location  of 
the  air  supply  intake  to  a  building  carries  with  it  a  great  re- 
sponsibility. Air  supplied  to  a  building  should  always  be 
taken  from  the  purest  source  possible,  and  when  this  supply 
is  known  to  be  bad  it  should  be  thoroughly  washed  before 
sending  through  the  ventilating  system. 

REFERENCES. — Trans.  A.  S.  H.  &  V.  E.  Studies  in  Air  Clean- 
liness, Vol.  XXI,  p.  211.  The  Problem  of  City  Dust,  Vol.  XXI, 
p.  225. 

Ozone  is  considered  by  some  to  be  effective  as  an  air 
purifier.  It  is  an  unstable  form  of  oxygen  probably  contain- 
ing a  greater  number  of  atoms  per  molecule  and  is  formed 
by  passing  air  through  a  highly  charged  electrical  field.  Be- 
cause of  its  instability  as  a  substance,  it  readily  breaks  up 
and  becomes  more  active  as  an  oxidizing  agent  than  oxygen 
itself.  In  its  decomposition  a  part  becomes  oxygen  and  the 
balance  is  said  to  enter  into  combination  with  substances  in 
the  air,  thus  cleansing  the  air  from  the'se  substances. 
Two  claims  are  made  for  ozone.  The  first  is  that  it  is  a  puri- 
fier, the  second  that  it  is  a  deodorizer.  The  first  has  not  been 
proved  satisfactorily,  but  the  second  is  substantiated  by 
many  proofs.  Ozone  without  doubt  conceals  odors,  but  it  is 
not  known  if  the  substances  producing  the  odors  are  ren- 
dered harmless  to  the  human  body. 

REFERENCES. — Trans.  A.  S.  H.  &  V,  E.  An  Experiment  with 
Ozone  as  an  Adjunct  to  Artificial  Ventilation  at  the  Mt.  Sinai 
Hospital,  N.  Y.  C.,  Vol.  XXI,  p.  256.  Air  Ozonation,  Vol.  XX, 
p.  337.  Ozone  and  Its  Applications,  Vol.  XIX,  p.  128.  H.  &  V. 
Mag.,  Ozone,  July,  1914,  p.  16. 

24.  Moisture  with  Air: — Moisture  in  the  atmosphere 
affects  the  comfort  of  the  occupants  as  well  as  the  efficiency 
of  the  heating  and  ventilating  system  in  any  room.  With 


HUMIDITY 


45 


moisture  in  the  room  a  person  may  feel  comfortable  when 
the  temperature  is  several  degrees  lower  than  the  comfort- 
able temperature  of  dry  air.  A  dry  atmosphere  takes  up 
moisture  from  the  room  furnishings  and  from  the  skin  sur- 
face of  the  occupants.  The  vaporization  of  moisture  from 
the  skin  causes  a  loss  of  heat  from  the  body  and  gives  to 
the  person  a  sense  of  cold  which  is  relieved  only  when  the 
temperature  of  the  room  is  increased.  An  atmosphere  that 
is  fairly  saturated  with  moisture  demands  little  evaporation 
from  the  skin,  in  which  case  the  body  retains  its  heat  and 
the  person  has  a  sensation  of  warmth  which  is  relieved  only 
by  lowering  the  temperature  of  the  air  of  the  room.  At  low 
temperatures  moisture  in  the  atmosphere  chills  the  surface 
of  the  skin  by  actual  contact.  This  is  not  as  noticeable 
when  the  air  is  dry.  It  follows  from  the  above  statements 
that  the  range  of  comfortable  temperatures  is  less  for  moist 


30  32  34  36  3S>  4O  42  44  46  48  5O  52   54   56   58  6O   62  64 

RELATIVE     HUMIDITY 
Fig-.   5. 


68  70  7Z  74  76  78 


air  than  for  dry  air.  The  Chicago  Commission  on  Ventila- 
tion, under  the  direction  of  Dr.  E.  Vernon  Hill,  developed  a 
series  of  curves  from  a  large  number  of  tests,  showing1  the 
best  relation  between  the  relative  humidity  and  the  comfort- 
able temperature  in  a  room  (See  Trans.  A.  S.  H.  &  V.  E.,  page 
607,  Vol.  XXIII).  The  curves  in  Fig.  5,  are  plotted  from  a 
summary  of  these  tests.  It  will  be  noted  that  the  condition 
represented  by  65°  and  55  per  cent,  humidity  is  as  satisfac- 
tory as  that  of  70°  and  35  per  cent,  humidity. 


HEATING  AND   VENTILATION 


In  addition  to  its  effects  upon  the  human  body,  moisture 
in  the  atmosphere  has  the  quality  of  storing  convected  heat. 
It  is  thus  a  better  heat  carrier  than  dry  air  and  is  a  benefit 
to  the  heating  and  ventilating  system  in  any  building. 

REFERENCES. — H.  &  V,  Mag.  The  Primary  Physiological 
Purpose  of  Ventilation,  Sept.  1913,  p.  35.  Metal  Worker. 
Humidity  and  House  Sanitation  Explained,  Jan.  24,  1913,  p. 
159.  Trans.  A.  S.  H.  &  V.  E.  The  Recirculating  of  Air  in  a 
School  Room  in  Minneapolis,  Vol.  XXI,  p.  109.  Relative 
Humidity,  Vol.  XVIII,  p.  106. 

25.  Humidity: — Absolute  humidity  is  the 
amount  of  moisture  mixed  with  the  air  at 
any  temperature,  expressed  in  grains  or  in 
pounds  per  cubic  foot.  Relative  humidity  is 
the  ratio  of  the  amount  of  moisture  actu- 
ally with  the  air  divided  by  the  amount  of 
moisture  which  the  same  volume  could 
hold  at  the  same  temperature  when  satu- 
rated. The  temperature  of  any  air  at  100 
per  cent,  saturation  (100  per  cent,  relative 
humidity)  is  called  the  dew  point.  Relative 
humidity  is  obtained  by  using  wet-and-dry 
bulb  thermometers  or  by  any  one  of  a  num- 
ber of  hygrometers  supplied  by  the  trade. 
The  wet-and-dry  bulb  hygrometer  has  a 
very  simple  application  and  is  generally 
used.  Having  given  two  thermometers 
Fig.  6.  (Fig.  6)  let  one  register  the  temperature  of 

the  room  air  and  the  other,  kept  wet  by  a  cloth  which  covers 
the  bulb  and  projects  into  a  vessel  filled  with  water,  a  tem- 
perature below  that  of  the  room  air.  If  the  air  is  saturated 
the  two  thermometers  will  record  the  same  temperature.  If 
the  air  is  not  saturated  the  thermometer  readings  will  differ 
according  to  the  humidity.  It  will  be  readily  seen  that  the 
lowering  of  the  mercury  in  the  wet  thermometer  is  due  to  the 
extraction  of  the  heat  from  the  mercury  column  in  vaporiz- 
ing the  moisture  from  the  bulb  to  the  air. 

In  taking  readings,  let  the  mercury  find  a  constant  level 
in  each  thermometer  and  note  the  difference  in  temperature 
between  the  two.  In  Table  12,  Appendix,  at  this  difference 


HUMIDITY 


47 


and  at  the  room  temperature  read  off  the  relative  humidity. 
Having  found  the  relative  humidity  take  from  Table  13, 
Appendix,  the  amount  of  moisture  with  saturated  air  at  the 
temperature  recorded  by  the  dry  thermometer  (absolute 
humidity  at  saturation).  Multiply  this  by  the  relative 
humidity  found  and  the  result  is  the  absolute  humidity  at 
the  given  relative  humidity,  i.  e.,  the  actual  amount  of 
moisture  with  the  air  per  cubic  foot  of  volume. 


Fig.  7. 


APPLICATION. — Room  air,  70°;  difference  in  readings,  6°. 
From  Table  12,  the  humidity  is  72  per  cent.  From  Table  13, 
col.  7,  .72  X  .001153  =  .00083  pounds  (5.81  grains)  per  cubic 
foot. 

Instruments  have  been  designed  giving  the  relative 
humidity  by  graphical  charts.  Fig.  7,  commonly  known  as 
the  hygrodeik,  shows  such  an  instrument.  To  find  the  rela- 
tive humidity  swing  the  index  hand  to  the  left  of  the  chart 
and  adjust  the  sliding  pointer  to  that  degree  of  the  wet 


48 


HEATING  AND   VENTILATION 


bulb  thermometer  scale  at  which  the  mercury  stands.  Swing 
the  index  hand  to  the  right  until  the  sliding-  pointer  inter- 
sects the  curved  line  extending  down- 
ward to  the  left  from  the  degree  of  the 
dry  bulb  thermometer  scale  indicated 
by  the  top  of  the  mercury  column  in 
the  dry  bulb  tube.  At  that  intersection 
the  index  hand  will  point  to  the  rela- 
tive humidity  on  the  scale  at  the  bot- 
tom of  the  chart.  Should  the  tempera- 
ture indicated  by  the  wet  bulb  ther- 
mometer be  60°  and  that  of  the  dry 
bulb  70°,  the  index  hand  will  indicate 
a  humidity  of  55  per  cent,  when  the 
pointer  rests  on  the  intersection  of  the 
GO0  wet  bulb  and  70°  dry  bulb  lines. 

The  instrument  in  most  general  use 
for  humidity  determinations  is  the 
Sling  Psychrometer  (See  Fig.  8).  This 
is  a  wet-and-dry  bulb  outfit  pivoted  to 
a  handle  in  such  a  way  that  the  ther- 
mometers may  be  revolved  through  the 
air  thus  causing  a  circulation  of  air 
Fig.  8.  over  them  The  wet  bulb  projects 

beyond  the  dry  bulb  and  is  covered  with  a  fine  mesh 
cloth.  This  cloth  is  dipped  into  distilled  water  and  the  ap- 
paratus revolved.  Read  the  mercury  level  frequently  and 
note  the  reading  of  each  thermometer  at  the  time  the  mer- 
cury in  the  wet  bulb  is  at  its  lowest  level.  For  accurate  work 
the  thermometers  should  meet  a  current  of  air  of  approximately  15 
feet  per  second,  according  to  government  recommendation. 

Table  12,  Appendix,  represents  U.  S.  Weather  Bureau 
Standards  and  is  used  as  a  reference  in  this  book.  Experi- 
ments by  Mr.  Willis  H.  Carrier,  presented  in  a  paper  to  the 
American  Society  of  Mechanical  Engineers  in  1911,  show 
humidities  differing  somewhat  from  Table  12  (See  "Psychro- 
metric  Charts"  following  Table  14,  Appendix). 

26.  Humidity  Chart: — For  close  approximations  the 
humidity  chart  (Fig.  9)  may  be  used  in  determining  relative 
humidity,  absolute  humidity,  dew  point,  temperature  of  wet 
bulb  and  temperature  of  dry  bulb.  On  the  left  of  the  chart 


HUMIDITY   DETERMINATION 


41) 


HYGROMETRIC     CHART 

GIVING 


140 


1O         20        30        40        50        60        70        80     •  90        100 

RELATIVE   HUMIDITY   IN    PER  CENT 

Fig".  9. 


Note. — Pig.  9  represents  two  charts  in  one.  First :  the  dry  bulb 
temperature  curve,  which  drops  to  the  left,  unites  with  the  wet  bulb 
and  relative  humidity  coordinates.  Second :  the  absolute  humidity 
curve,  which  rises  to  the  left,  unites  with  the  dry  bulb  and  relative 
humidity  coordinates.  This  makes  it  possible  to  use  the  two  charts  as 
one,  through  the  relative  humidity  scale  which  is  common  to  both. 


50  HEATING  AND  VENTILATION 

is  a  scale  referring-  to  horizontal  lines  giving  temperatures 
of  the  wet  bulb.  The  scale  on  the  right,  referring  to  the 
lines  curving  downward  from  right  to  left,  is  the  tempera- 
ture scale  of  the  room,  or  dry  bulb  temperature.  The  scale 
along  the  bottom  of  the  chart  gives  the  relative  humidity. 
The  scale  of  numbers  up  the  center  of  the  chart  refers  to 
the  lines  curving  downward  from  left  to  right  and  indicates 
absolute  humidity.  For  illustration,  assume  a  dry  bulb  tem- 
perature of  70°  and  a  wet  bulb  temperature  60°,  and  find 
relative  humidity,  absolute  humidity  and  temperature  of  the 
dew  point.  Starting  on  the  right  hand  scale  at  70,  follow 
down  the  room  temperature  curve  until  it  crosses  the  hori- 
zontal line  of  60°  wet  bulb  temperature.  From  this  intersec- 
tion drop  to  the  relative  humidity  scale  and  read  there  55 
per  cent.  To  obtain  the  absolute  humidity  trace  up  the  rela- 
tive humidity  line  to  its  intersection  with  the  70°  abscissae 
(horizontal  line  through  70°)  and  obtain  4.4  grains  per  cubic 
foot.  If  the  room  air  should  drop  in  temperature,  the  abso- 
lute humidity  would  remain  the  same  until  the  dew  point  is 
reached  (neglecting  air  contractions).  Tracing  down  the 
4.4  grain  line  to  100  per  cent,  relative  humidity  gives  the 
room  temperature  52°.  This  shows  that  if  so  cooled  the  air 
begins  depositing  moisture  at  this  temperature.  If  the  tem- 
perature of  the  room  air  should  increase  to  90°,  the  relative 
humidity  may  be  obtained  by  following  the  4.4  grain  line  to 
its  intersection  with  the  90°  abscissae  line  of  room  tempera- 
ture and  from  this  intersection  dropping  to  the  relative 
humidity  scale  at  31  per  cent.  Thus,  having  air  under  any 
set  of  temperature  and  humidity  conditions,  the  effect  that 
a  change  in  any  one  condition  would  have  upon  the  others 
may  be  obtained  without  calculations. 

APPLICATION  1. — The  air  of  a  room  gives  a  dry  bulb  read- 
ing of  80°  and  a  wet  bulb  reading  of  69°.  What  is  the  rela- 
tive humidity? 

Solution. — Find  intersection  of  dry  bulb  curve  and  wet 
bulb  abscissae.  From  such  intersection  drop  perpendicular  to 
relative  humidity  scale  and  read  57.5  per  cent.  Check  by 
Table  12,  Appendix:  80°  room  temperature  and  11  degrees 
difference  gives  57  per  cent,  relative  humidity. 

APPLICATION  2. — In  the  above  problem  determine  the  num- 
ber of  pounds  of  water  vapor  in  the  room  if  its  capacity  is 
3500  cubic  feet? 


HUMIDITY  DETERMINATION  51 

Solution. — At  the  intersection  of  the  80°  and  58  per  cent. 
coordinates,  read  absolute  humidity  in  grains  of  moisture  per 
cubic  foot  as  6.2.  Total  moisture  in  room  =  3500  X  6.2  = 
21700  grains,  or  21700  -H  7000  =  3.1  pounds  of  water  in  form 
of  vapor.  Check  by  Table  13,  Appendix.  From  this  table, 
column  7,  the  weight  of  the  vapor  in  pounds  present  at 
saturation  at  80°  is  by  interpolation,  .001578  per  cu.  ft.  At  57 
per  cent  relative  humidity  each  cubic  foot  would  contain 
.001578  X  .57  —  .000899  pound  and  3500  cubic  feet  would  con- 
tain 3.15  pounds.  , 

APPLICATION  3. — To  what  temperature  could  this  room  be 
cooled  before  moisture  would  be  deposited  from  the  air,  i.  e., 
at  what  temperature  of  the  air  would  the  dew  point  be 
reached? 

Solution. — The  dew  point  for  this  room  air  is  the  tem- 
perature at  which  6.2  grains  of  moisture  per  cubic  foot  rep- 
resents saturation,  or  100  per  cent,  relative  humidity.  There- 
fore follow  the  6.2  grain  line  to  intersection  with  the  100 
per  cent,  vertical  and  read  63°.  Check  by  Table  11,  Appendix. 
Temperature  at  which  6.2  grains  moisture  becomes  the  sat- 
uration quantity  is  by  interpolation,  62.3°. 

APPLICATION  4. — To  what  temperature  could  this  room  be 
heated  without  moisture  addition  or  loss  and  maintain  a 
relative  humidity  of  not  less  than  50  per  cent? 

Solution. — Following  the  6.2  grain  line  to  intersection 
with  50  per  cent,  ordinate,  read  from  the  right  the  room  tem- 
perature, 85°.  Check  by  Table  11,  Appendix.  Since  6.2 
grains  at  the  temperature  sought  will  be  50  per  cent,  of  the 
moisture  of  saturation  at  that  temperature,  12.4  grains 
would  be  saturation  quantity,  which  from  Table  11  by  inter- 
polation corresponds  to  84.2°. 

27.  Theoretical  Amount  of  Moisture  to  be  Added  to  Air 
to  Maintain  a  Certain  Humidity: — Warm  air  has  a  much 
greater  capacity  for  holding  moisture  than  cold  air.  When 
air  of  a  given  outside  temperature  is  heated  for  interior 
service,  the  volume  increases  with  the  absolute  temperature 
(See  Art.  15).  On  the  other  hand,  the  relative  humidity  de- 
creases rapidly  as  shown  by  the  humidity  curves  (Fig.  9). 
Air  that  is  dry  is  unpleasant  to  the  occupants,  as  well  as 
being  detrimental  to  the  furnishings  of  the  room.  Therefore, 
some  means  should  be  provided  to  supply  moisture  to  the 
incoming  air  current.  In  calculating  the  amount  to  be 


HEATING  AND   VENTILATION 


added,  let  Q  =  cubic  feet  of  air  per  hour  entering  the  room 
at  the  register  temperature  t,  Q'  =  corresponding  volume  at 
room  temperature  t'  and  humidity  u' ,  Q»  =  corresponding 
volume  at  outside  temperature  to  and  humidity  «o.  Also  let 
T,  7"  and  To  be  the  absolute  temperatures  of  the  entering  air, 
room  air  and  outside  air  respectively.  From  the  equations 
TQ'  =  T'Q  and  TQo  -  T0Q  (17) 

find  Q'  and  Qo.  From  Tables  11  or  13,  Appendix,  find  the 
amounts  of  moisture  Mf  and  Mo  in  one  cubic  foot  of  saturated 
air  at  the  temperatures  t'  and  to,  multiply  these  by  the  re- 
spective humidities  and  volumes,  and  the  difference  between 
the  two  final  quantities  will  be  the  amount  of  moisture  re- 
quired per  hour  as  expressed  by  the  equation 

W  =   Q'M'u'  —  QoMoUo  (18) 

APPLICATION. — Let   Q    =    5000,   t    =    130,   t'    =    70,    to    =    30, 
u'  =  .50,  uo  -   .50,  M'   =   7.98  and  .1/0   =    1.935,  then 
(/   =  5000   X    530  -i-   590   =   4490 
Qo  =  5000   X   490  -i-   590  =   4154 
W  =  13896  grains,  or  1.983  Ibs.  per  hr. 

This  means  that  approximately  2  pounds  of  water  would  be 
evaporated   for   every   5000   cubic   feet   of   fresh   air   entering 
the    room    under    the    above    conditions    (See 
__,£    also  application  in  Art.  72). 

2S.  Velocity  in  the  Convection  of  Air  by 
!  the  Application  of  Heat: — Let  1\<>  (Fig.  10)  be 
the  height  of  the  chimney  or  stack.  If  the 
temperature  of  the  gases  within  the  chimney 
CD  be  the  same  as  that  of  the  entering  air 
there  will  be  no  natural  circulation,  because 
the  column  CD  will  just  balance  a  corre- 
sponding column  All  upon  the  outside.  If  the 
temperatures  of  the  chimney  gases  CD  and 
entering  air  be  tr  and  to  respectively,  the 
chimney  gases  being  (tc  —  to)  degrees  above 
that  of  the  outside  air,  then  upon  entering  the 
chimney  the  air  becomes  less  dense  and  ex- 
pands according  to  the  ratio  of  the  absolute 
C  temperatures  before  and  after  heating.  With 
Fig.  10.  an  outside  column  of  Jio  feet,  it  will  require 

a  column  of  the  chimney  gases  7?«  +  'ic  feet 'to  produce 
equilibrium.  In  other  words,  the  equivalent  column  of  gases 


MEASUREMENT   OP  AIR  VELOCITY  53 

producing  circulation  in  the  chimney  has  a  height  of  he  feet. 
Assume,  in  the  system  ABCDE,  that  the  interior  cross  sec- 
tions at  all  points  are  uniform.  The  volumes  of  AB  (imag- 
inary column)  and  CE  (actual  column)  are  to  each  other  as 
their  respective  heights,  and 

Vo  :  Vo  +  Vc  ::  ho  :  ho  +  lie,  or  ho  :  460  +  to  ::  ho  +  ho  : 
460  +  tc.  From  this  we  obtain  hc  (460  +  to)  =  ho  (tc  —  to) 
and 

ho   (tc  —  to) 


460  + 


(19) 


Substituting  for  li  in  the  equation  v  =  V2  yh,  its  correspond- 
ing value  he,  we  have 


v  =  V2  yhc  — 


460  +  to 

It  is  found  in  practice  that  the  theoretical  velocity  as 
given  by  this  equation  is  never  obtained  because  of  the  loss 
of  draft  due  to  the  friction  between  the  column  of  gases  and 
the  sides  of  the  chimney,  and  from  wind  pressures  and 
other  causes.  Some  engineers  estimate  the  actual  discharge 
from  the  chimney  at  50  per  cent,  of  the  theoretical.  This 
estimate  may  be  fairly  safe  for  medium  sized  chimneys  but 
will  not  be  realized  on  the  smaller  ones  used  in  residences, 
which  will  probably  be  25  to  50  per  cent,  of  the  theoretical. 
As  the  transverse  net  area  becomes  smaller,  the  percentage 
of  friction  to  the  total  air  moved  increases  very  rapidly  and 
soon  becomes  the  principal  factor.  Prof.  Kent  assumed  a 
layer  of  gases  two  to  three  inches  thick  next  to  the  interior 
surface  as  having  no  velocity  and  consequently  ineffective. 
Thus  a  minimum  of  4  inches  would  be  added  to  each  theoret- 
ical cross  dimension  to  obtain  the  nominal  size  of  a  rec- 
tangular chimney. 

Some  uncertainty  will  be  experienced  in  the  selection  of 
the  best  values  for  the  average  temperatures  of  the  chimney 
gases,  tc,  and  the  outside  temperature,  to,  for  calculations. 
tc  is  low  for  residence  chimneys  because  of  the  low  rate  of 
combustion  (3  to  7  Ibs.  per  sq.  ft.  of  grate  per  hr.)  and  high 
for  large  apartment  houses,  office  buildings  and  power 
plants  (10  to  24  Ibs.  per  sq.  ft.  of  grate  *)er  hr.).  It  is  low 
for  unprotected  chimneys  having  large  heat  loss  from  radia- 
tion and  high  for  those  that  are  housed-in  with  the  build- 


54 


HEATING  AND  VENTILATION 


ing.  Assume  to  =  70  for  all  calculations.  Approximate 
values  for  chimney  height  above  the  grate,  ho,  average  tem- 
perature of  gases  in  chimney,  tc,  and  temperature  of  gases 
entering  chimney,  tb,  may  be  taken  as  in  Table  V. 

TABLE  V. 


Residences 

Apartment  houses 

ho 

30 

40 

50 

60 

f 

200 

225 

260 

300 

to 

300 

350 

400 

450 

To  estimate  the  approximate  volume  of  gases  circulating 
through  the  chimney  per  second,  multiply  the  pounds  of  coal 
burned  per  hour  by  25  (pounds  of  gases  per  pound  of  coal, 
maximum)  times  the  specific  volume  of  the  gas  at  the  tem- 
perature of  the  entering  chimney  gases  and  divide  the  result  by 
3600.  Note  that  the  average  temperature  of  the  gases  is 
used  in  obtaining  draft  but  that  the  entering  temperature  is 
used  in  obtaining  area,  since  all  transverse  areas  are  equal 
and  calculated  to  carry  the  gases  at  the  entering  volume. 

When  Equation  20  is  applied  to  hot  air  stacks  in  heating  sys- 
tems, allowances  for  friction  are  much  less  because  of  the 
smooth  interior  of  the  duct.  In  such  cases  the  actual  veloc- 
ity of  the  air  should  approach  more  nearly  the  theoretical. 
(For  applications  to  chimneys  see  Arts.  31  and  32). 

29.     Measurement  of  Air  Velocities: — (See  also  Arts.  144- 
146).      In   ventilating   work    it   is   often   of  the   greatest    im- 
portance to  determine  air  velocities  accurately.     The  correct 
selection  of  the  sizes  of  air  propelling  fans  or  blowers  to  do 
a  given  work  depends  largely  upon  the 
measurement  of  the  velocity  of  air  de- 
livery.     In   acceptance   and   other   tests 
this  measurement  is  equally  important. 
Velocities  are  most  commonly  meas- 
ured by  means  of  a  vane  wheel  instru- 
ment called  the  anemometer.     It  is  essen- 
tially a  delicately  pivoted  wheel  having 
from  six  to  fifteen  vanes  and  similar  to 
the  common  wind  mill  wheel   (See  Fig. 
11).      To    the    shaft    is   connected   a   re- 
cording mechanism  consisting  of  a  set 
Fig.  11.  of  dials  which  show  the  velocity  of  the 


MEASUREMENT  OF  AIR  VELOCITY 


55 


air  traveling  past  the  instrument.  By  reading  this  recording 
mechanism  against  a  stop  watch  the  velocity  of  the  air  per 
unit  of  time  may  be  obtained.  Since  the  instrument  works 
against  the  friction  of  moving  parts  its  readings  are  sub- 
ject to  variation  and  even  with  frequent  calibrations  it  is 
not  wholly  to  be  relied  upon.  Various  tests  of  anemometers 
in  comparison  with  the  absolute  readings  of  a  gas  tank 
have  shown  errprs  as  high  as  35  per  cent,  slow  to  14  per  cent, 
fast,  in  the  discharge  from  pipes  8  inches  to  24  inches  in 
diameter.  It  is  not  fair  to  condemn  a  type  of  instrument 
because  some  instruments  of  the  class  have  failed  through 
long  service  or  lack  of  care,  but  in  general  it  is  safe  to  say 
that  the  anemometer  as  an  instrument  for  delicate  velocity 
measurement  should  be  used  with  great  care  and  should  be 
frequently  calibrated. 

Velocities  are  also  measured  by  the  Pitot  tube,  Fig.  12. 
This  method  of  measurement  is  not  as  simple  as  the  ane- 
mometer but  when  properly  applied  it  is  more  accurate.  The 
Pitot  tube  is  essentially  a  pressure  measurer.  In  every  mov- 
ing fluid  (liquid  or  gas)  three  pressures  are  acting.  These 
are  commonly  designated  dynamic,  static  and  velocity.  Let  the 


Fig.  12. 

bent  tube  A  be  partially  filled  with  mercury,  oil  or  water  as 
shown  and  let  it  be  inserted  in  the  pipe  with  the  open  end 
square  against  the  stream.  Also,  let  tube  B  be  similarly 
constructed  but  let  the  plane  of  the  opening  be  90  degrees 
to  A.  Tube  A  is  acted  upon  inside  the  pipe  by  the  atmos- 
phere plus  the  total  forward  pressure  of  the  stream  (dy- 
namic pressure)  and  on  the  outside  by  the  atmosphere. 
Tube  B  is  acted  upon  inside  the  pipe  by  the  atmosphere  plus 
the  cross  pressure  (static  pressure)  and  on  the  outside  by 
the  atmosphere.  In  each  case  the  liquid  in  the  bent  tube 
Shows,  unequal  levels,  A  having  greater  depression  than  B. 


56  HEATING  AND  VENTILATION 

Now  if  the  two  tubes  are  united  as  in  C  so  that  the  pipe 
pressures  act  on  opposite  sides  of  the  same  liquid  column, 
the  atmospheric  pressure  is  eliminated  and  the  two  internal 
pressures  subtract,  giving  velocity  pressure,  i.  e., 

dynamic  pressure  —  static  pressure   =   velocity  pressure. 

C  shows  the  instrument  as  commonly  applied.  In  this  the 
subtraction  is  automatic  and  the  difference  in  levels,  hw,  is 
caused  by  the  velocity  pressure  only.  To  find  the  actual 
velocity  of  the  air  in  the  pipe  apply  the  equation  v  =  V2  gh 
where  v  =  velocity  in  feet  per  second,  g  =  acceleration  of 
gravity  in  feet  per  second,  per  second  and  h  —  the  velocity 
head  of  the  air  in  feet.  If  the  tube  contains  water  at  60°, 
the  ratio  between  the  specific  gravities  of  air  and  water  be- 

62.37 

ing  —      -  =   816.4   (See  Tables  9  and  13.  Appendix),  the  equa- 
.0764 

tion  reduces  to 


v   =    V2   X   32.16   X   816.4   X   hw   -±   12  or 

o   =    66.2  \/h~  (21) 

where  hw  =  the  difference  in  height  in  inches  of  the  water 
columns  with  both  legs  connected  as  described  and  at  a  tem- 
perature of  60°.  By  a  similar  method  this  equation  may  be 
deduced  for  a  mercury  or  other  liquid  column,  or  for- other 
temperatures  than  60°. 

Several  Pitot  tubes,  differing  from  each  other  slightly  in 
features  of  design,  are  in  commercial  use.  Because  of  these 
mechanical  differences  their  readings  do  not  absolutely 
check  each  other  or  those  from  the  theoretical  formula, 
hence  all  readings  must  be  multiplied  by  a  constant  charac- 
teristic of  the  tube  in  use  (See  Trans.  A.  S.  II.  &  V.  E.,  Vol. 
XXI,  p.  459). 

In  using  the  Pitot  tube  or  the  anemometer,  the  fact 
should  not  be  lost  sight  of  that  the  velocity  varies  from  a 
minimum  at  the  inner  surface  of  the  pipe  to  a  maximum  at 
the  center.  The  friction  on  the  inner  surface  causes  the 
moving  fluid  to  be  retarded  next  the  pipe  wall  and  any  test 
for  velocity  must  account  for  this  variation.  With  a  circular- 
pipe  the  change  of  velocity  may  be  approximately  repre- 


MEASUREMENT   OP   AIR   VELOCITY  57 

sented   by  the  abscissae  of  a  parabola  with   its  axis   on   the 
axis  of  the  circular  pipe   (See  Fig-.   13). 

The  point  of  average  velocity  is  variously  quoted  from 
one-fourth  to  one-third  the  radius  from  the  wall  toward  the 
center,  the  value  depending  probably  upon  the  character  of 
the  inner  surface  of  the  tube.  For  general  use  three-tenths 
will  give  good  average  values.  For  conduits  of  other  shapes 
the  position  of  mean  velocity  is  difficult  to  determine.  The 
only  safe  way  is  to  divide  the  cross  section  into  small  areas 
and  take  readings  in  each  area  to  obtain  the  average.  This 


Fig-.  13. 

variation  of  velocity  from  the  center  of  the  stream  lessening 
toward  the  walls  may  possibly  account  for  many  of  the 
variations  shown  by  anemometer  tests.  It  is  evident  that 
it  is  difficult  to  locate  an  anemometer  so  that  it  will  give 
the  correct  average  reading-.  In  large  ducts  the  error  will 
be  less.  Pitot  tube  measurements  are  more  easily  applied 
and  are  more  reliable. 

Automatic  recording  meters  may  be  obtained  for  keep- 
ing permanent  records  of  the  flow  of  air  and  steam  through 
ducts  and  pipes.  The  record  from  the  meter  indicates  di- 
rectly the  cubic  feet  of  free  air  or  other  fluid  circulating 
during  each  hour  of  the  day. 

REFERENCES.— Kent,  Mechanical  Engineers  Pockct-Book.  Trans. 
A.  S.  H.  &  V.  E.  Report  of  the  Committee  on  the  Best  Way 
to  Take  Anemometer  Readings,  Vol.  XIX,  p.  202.  On  Stand- 
ardization of  Use  of  Pitot  Tube,  Vol.  XX,  p.  210.  Measure- 
ment of  Air  Flow,  Vol.  XXI,  p.  450.  Trans.  A.  S.  M.  E.  Meas- 
urement of  Air  in  Fan  Work,  Vol.  XXXIV,  p.  1019.  The 
Pitot  Tube,  Vol.  XXV,  p.  184.  Jour.  A.  S.  M.  E.  Pitot  Tubes 
for  Gas  Measurement,  Sept.  1913,  p.  1321. 

30.  To  Determine  the  Transverse  Area  of  a  Chimney 
for  Any  Given  Heig-ht: — The  value  of  any  flue  as  a  carrier 


58  HEATING  AND  VENTILATION 

of  heated  gases  depends  upon  both  velocity  and  transverse 
area.  It  is  not  only  necessary  that  a  chimney  have  suffi- 
cient height  to  produce  draft  but  it  must  have  an  area 
capable  of  carrying-  the  total  volume  of  the  gases.  The 
height  may  be  sufficient  to  create  a  good  velocity  but  the 
area  may  not  be  sufficient  to  carry  the  volume  of  gases 
required  and  the  draft  becomes  ineffective  because  of  clog- 
ging. On  the  other  hand,  the  draft  may  become  ineffective 
from  reduced  velocity  due  to  too  large  an  area.  In  any 
chimney,  height  and  area  are  dependent  variables.  The 
height  is  first  determined  to  give  a  certain  draft  and  to 
agree  with  surrounding  building  conditions,  after  which 
the  area  is  determined  to  carry  the  gases  at  the  given 
chimney  height  and  resulting  gas  velocity.  To  obtain  the 
theoretical  size  of  a  chimney,  substitute  Jio  and  the  assumed 
values  of  tc  and  to  in  Equation  20  and  determine  the  velocity 
of  the  gases  per  second.  Divide  the  estimated  maximum 
volume  of  gases  moved  per  second  by  the  velocity  to  de- 
termine the  transverse  area  in  square  feet  and  reduce  this 
value  to  a  corresponding  round,  square  or  rectangle.  For 
the  actual  size  add  a  minimum  of  4  inches  to  each  theoretical 
dimension. 

31.  Small  Chimneys: — Application  for  a  ten  room  residence. 
Given:  total  heat  loss  from  the  building  per  hour  100000  B.  t. 
u.,  coal  13500  B.  t.  u.  per  pound,  furnace  efficiency  60  per  cent, 
temperature  of  chimney  gases  at  base  of  chimney  300°, 
average  temperature  of  chimney  gases  200°,  outside  tem- 
perature 70°  and  height  of  chimney  30  feet  above  the  grate. 

A  heat  loss  of  100000  B.  t.  u.  per  hour  will  require 
100000  -=-  (13500  X  -60)  zr  12.35  pounds  of  coal  per  hour  at 
the  grate.  With  gases  300°  temperature  there  will  be  moved 
12.35  X  25  X  19.14  =  5933.4  cubic  feet  of  gases  per  hour. 
The  velocity  of  the  chimney  gases  according  to  equation  is 
21.8  feet  per  second,  which  gives  144  X  5933.4  -4-  (3600  X 
21.8)  =  10  square  inches,  or  3.2-in.  X  3.2-in.  Adding  4  inches 
to  each  dimension  =  7.2-in.  X  7.2-in.,  say  8.5-in.  X  8.5-in. 
to  fit  the  brick  work.  If  this  were  an  outside  wall  chimney 
it  should  be  8.5-in.  X  13-in. 

Application  for  an  apartment  house  or  small  school.  Given: 
total  heat  loss  from  the  building  per  hour  1000000  B.  t.  u., 
Jio  =  60,  tc  —  300,  1i>  —  450,  to  =  70,  and  the  coal  and  air  con- 
ditions as  above,  find  the  sizes  of  the  chimney,  8.5-in.  X  8.5- 


CHIMNEYS  59 

in.    (theoretical)   and   13-in.    X    13-in.    (actual).     For  an  out- 
side chimney,  at  least  13-in.   X   17.5-in. 

In  small  chimney  construction  there  is  a  tendency  to 
leave  the  interior  of  the  brick  work  very  rough.  This  should 
not  be,  but  where  such  methods  are  allowed,  one  dimension 
of  the  actual  sizes  determined  as  above  should  be  increased 
by  the  width  of  one  brick. 

32.  Large  Chimneys: — Chimneys  for  office  buildings, 
power  plants,  etc.,  are  generally  rated  in  terms  of  boiler 
horse-power.  To  calculate  the  sizes  of  such  chimneys,  first 
find  the  intensity  of  draft  (pressure  of  the  current  of  gases 
in  inches  of  water,  determined  by  a  draft  gage).  This  will 
vary  from  .75  in.  to  1.25  in.,  according  to  the  type  of  boiler, 
method  of  firing,  and  length  and  size  of  breeching.  See 
books  on  power  plant  operation.  Having  the  draft,  find 
the  height  of  the  chimney,  ho,  by  the  equation 


po  f 

\  T2  T! 


d  —  .52  h0  p0  f  (22) 


where  d  =  draft  in  inches  of  water,  p0  =  observed  atmos- 
pheric pressure  (commonly  taken  14.7),  T2  =  absolute  tem- 
perature of  outside  air  and  7\  =  absolute  temperature  of 
gases  in  chimney.  Having  ho,  find  the  diameter  of  a  round 
chimney  by  the  equation 

B.  H.  P.   =   2.4  D2  ^ho~  (23) 

where  B.  H.  P.  =  nominal  boiler  horse-power  and  D  = 
diameter  of  chimney  in  feet.  For  square  chimneys  find  the 
equivalent  area  of  the  round  chimney. 

APPLICATION. — Find  the  height  and  diameter  of  a  chim- 
ney for  1000  boiler  horse-power.  Temperature  of  gases 
500°,  outside  air  70°  and  required  draft,  1-inch  of  water. 
In  Equation  22 

(1               1 

530           960 
ho   =    150  ft. 
Also  substituting  in  Equation  23 

1000    =    2.4  D2V150 

D   =   5.8  ft.,  say  6  ft. 

33.  Chimney  Notes: — The  ideal  chimney  flue  is  round  in 
section.  Most  building  construction,  however,  requires  rec- 
tangular shapes.  These  should  be  kept  as  nearly  square  as 
possible..  No  chimney  flue  should  be  built  less  than  8-in.  x 


60  HEATINC    AND    VENTILATION 

8-in.  All  chimneys  should  be  built  up  of  Imnl  hnni«l  brirk* 
well  bedded  in  cement  mortar.  All  joints  should  be  struck 
smooth.  Interiors  arc  improved  if  lined  with  hard  burned  flue 
tiles.  Chimneys  should  be  built  free  from  other  house  con- 
struction so  as  to  permit  the  unequal  expansion  and  con- 
traction without  cracking  the  walls  of  the  house  or  the 
chimney.  The  top  of  the  chimney  should  extend  above  the 
highest  point  of  the  building.  If  the  top  is  below  any  near- 
by portion  of  the  building,  eddy  currents  will  be  formed 
which  will  enter  the  top  of  the  flue  and  seriously  reduce 
the  draft.  Under  such  conditions  a  shifting  cowl  may  be  ad- 
visable. Chimneys  under  30  feet  in  height  are  unreliable  in 
.their  action.  Some  engineers  recommend  nothing  under  40 
feet.  The  chimney  should  have  no  other  openings  into  it 
than  the  furnace  or  boiler  smoke  pipe.  Chimneys  in  outside 
walls  are  not  as  satisfactory  as  when  built-in,  due  to  the 
chilling  effect  of  the  outside  air.  When  an  outside  wall  chim- 
ney is  put  in  it  should  be  made  double  walled  with  air  space 
between  the  walls.  A  warm  air  flue  by  the  side  of  a  chim- 
ney is  an  ideal  location  for  the  flue.  All  chimneys  should 
rest  upon  solid  foundations.  All  joints  between  the  boiler 
and  the  chimney  should  be  tight  to  preserve  the  draft.  Good 
draft  is  very  essential  to  the  success  of  any  type  of  heating 
system,  and  the  purchaser  should  be  required  to  guarantee 
a  sufficient  draft  and  capacity  of  his  chimney  before  the 
manufacturer  should  be  expected  to  guarantee  a  stated  rat- 
ing of  his  furnace,  heater  or  boiler. 

REFERENCES. — Christie,  Chimney  Design,  Gebhardt,  Steam 
Power  Plant  Engineering,  Marks,  Mechanical  Engineers  Handbook, 
Kent,  Mechanical  Engineers  Pocket-Book,  H.  &  V.  Mag.  Baldwin 
on  Chimneys,  Oct.  1913,  p.  23,  Jan.  1914,  p.  31. 

34.  Cowls  and  Ventilator  Heads: — The  capacity  of  any 
vent  or  chimney  flue  may  be  increased  by  properly  designed 
cowls  surmounting  the  top  of  the  opening.  Much  of  the 
down  draft  experienced  under  changing  wind  pressures  may 
thus  be  eliminated.  Shifting  heads  or  cowls  take  advantage 
of  any  wind  velocity  to  increase  the  upward  movement  of 
the  air  by  induction  and,  when  fitted  with  bearings  that  per- 
mit adjustment  from  the  slightest  wind  velocity,  may  be 
considered  highly  desirable. 


CHAPTER  III. 


HEAT   LOSSKS   FROM    BUILDINGS 


35.  Heat    Dissipated    from    Iliiildi  niis : — In    planning"    the 
heating  system   for  any   building-,   the  first   and   most   impor- 
tant  part  of  the   work   is   to   estimate   the   total   heat   lost   in 
B.    t.    u.    per   hour   from   building.      Unfortunately   this   is   the 
part   which   is   open  to   the   least  satisfactory  calculation   be- 
cause of  varying  wind  conditions  and  imperfections  in  build- 
ing- construction,   and   because  of  the   lack   of  accurate   con- 
ductivity values,  especially  those  relating  to  the  more  recent 
building  materials. 

Heat  is  lost  from  a  building  in  three  ways:  first,  that 
transferred  through  the  walls,  windows  and  other  exposed 
building  materials  by  conduction  and  lost  by  radiation  and 
convection;  second,  that  carried  away  by  convection  air  cur-* 
rents  that  pass  out  through  wall  cracks  and  door  and  win- 
dow openings  to  the  outside  air;  third,  that  lost  through 
specially  prepared  ventilating  ducts.  The  third  item  is  not 
included  in  the  usual  building  heat  loss  (See  Arts.  41  and  42). 
In  the  average  building  the  conduction  loss  is  the  principal 
one,  although  it  is  now  found  that  the  convection  loss  is  of 
much  more  importance  than  has  been  generally  considered. 
In  any  case  neither  of  these  losses  can  be  determined  ex- 
actly, but  close  estimations  may  be  made. 

36.  Conduction  and  Radiation  Losses: — These  losses  are 
considered    under  various   heads,    such   as   glass,   wall,    floor, 
ceiling  and  door  losses.     Available  data  have  been  obtained 
by  experimentation  but  these  do  not  agree  very  closely.     The 
reason  for  so  rmich  uncertainty  in  this  part  of  the  heating- 
work  is  found  in  the  fact  that  there  are  great  differences  in 
methods    of    building    construction.      Conductivity    tests    on 
simple  materials  give  fairly  uniform  results,  but  when  these 
same  materials  are  assembled  in  building  walls  the  quality 
of  the   workmanship   often   permits   more   heat   loss  by  con- 
vection   than,  would    be    transmitted    through    the    materials 
by  conduction.      The   values  quoted   for   glass   and   the   more 
compactly    built    up    structures    such    as    brick    walls,    agree 
fairly  well.      The  greatest   difficulty   is   found   in   the   balloon 
frame   building   with   its   studded   walls,   where   the   dead   air 
space    in   a   well    constructed    wall    may   be   a   good    noncon- 


HEATING  AND   VENTILATION 


a  D  c 


ductor,  or  where  on  the  other  hand  the  same  space  in  a 
poorly  constructed  wall  may  become  a  circulating  air  space 
to  cool  the  walls  by  the  movement  of  the  air. 

As  an  illustration  of  what  may  be  expected  in  building 
losses  let  Fig-.  14  represent  a  4-inch  studded  wall  with  a 
tight  air  space  between  the  studding.  It  is  built  up  of  ma- 
terials each  having  a  different  conductivity  and  is  sub- 
jected upon  one  side  to  the  room  temperature  t'  and  upon  the 
other  to  the  outside  temperature  to.  Let  aa'  ,  &&',  cc',  etc.,  be 

planes  of  equal  temperature,  but 
each  plane  having  less  inten- 
sity of  temperature,  in  the  order 
named,  between  t'  and  to.  Also 
let  the  curve  xyz  represent  the 
temperature  drop  (measured  on 
the  ordinates  above  an  arbi- 
trary zero,  not  marked)  in  the 
heat  travel  between  the  enter- 
ing and  leaving  radiant  heat 
rays,  x  and  z.  It  will  be  noticed 
that  the  temperature  drop  is  not 
uniform  along  the  path  of  heat 
travel.  This  is  because  of  the 
varying  conductivities  of  the 
different  materials  passed 
through.  Along  every  heat  path 
there  are  three  resistances  to 


d  t>  c 


-  14- 


the  flow  of  heat  between  t'  and  to',  the  air  envelope 
in  contact  with  the  wall,  the  materials  composing  the 
wall  and  the  surfaces  of  each  material  composing  the 
wall.  The  summation  of  these  resistances  represents 
the  insulating  effect  against  heat  flow.  It  is  desir- 
able that  these  resisting  surfaces  and  materials  be  of 
such  a  character  as  to  cut  off  heat  flow  across  the  wall  as 
completely  as  possible.  The  common  defect  found  with  such 
wall  combinations  is  loose  construction  and  air  circulation  be- 
tween the  studding.  Since  the  insulating  effect  of  any  ma- 
terial or  combination  of  materials  is  proportional  to  the 
total  resistance  along  the  heat  path,  free  air  circulating  be- 
tween the  studding,  say  from  basement  to  attic,  would  cause 
an  increased  heat  loss  because  the  resistances  through  the 
latter  half  of  the  wall  would  be  eliminated.  If,  in  Fig.  14, 


HEAT  LOSSES  FROM  BUILDINGS  63 

the  air  space  marked  stud  were  not  tightly  closed  at  bottom 
and  top,  the  heat  crossing  from  ccf  to  dd'  would  be  carried 
away  by  convection  and  the  insulating-  qualities  of  the  wall 
would  be  R'  as  compared  with  R  in  a  tight  wall.  Still  air 
is  a  good  nonconductor.  Convected  air  is  a  good  heat  car- 
rier. Walls  of  other  construction  give  less  uncertainty  in 
heat  calculation. 

Theoretical  equations  for  heat  losses  through  building 
walls  are  based  upon  conductivity  values  (reciprocals  of  re- 
sistances per  unit  thickness)  of  the  various  materials  and 
do  not  take  into  account  such  incidental  points  as  interven- 
ing air  spaces  and  poor  construction.  Since  the  amount  of 
heat  transmitted  is  equal  to  the  temperature  drop  divided  by  the  sum 
of  the  resistances,  we  have  for  any  combination  of  materials 
(assuming  all  surfaces  in  contact  and  no  air  spaces),  Hu  = 

(tf  —  to)    -f    (R«  +  Rb  +  Re   +   +   #1  +  R2  +  Ra  +  ), 

where  Ra,  Rb,  Ra,  etc.,  are  the  resistances  of  the  materials 
and  7?i,  R2,  R3,  etc.,  are  the  surface  resistances  per  unit  area. 
With  the  material  thicknesses  m,  n,  o,  etc.,  and  the  conduc- 
tivities Ku,  Kb,  Kc,  Ki,  K2,  K3  respectively. 

V  —  to 

Hu (24) 

m          n  o  111 

+ + +  + + +  — ,  etc. 

Ka        Kb        Kc  K-L        K2        K3 

Collecting  the  conductivities  in  the  denominator  and  placing 
the  reciprocal  of  this  summation  as  the  combined  conductivity 
(rate  of  transmission  per  unit  area),  K,  we  have  for  any 
area,  A, 

H  =  K  A   (V  —  to)  (25) 

Equation  24  is  developed  to  illustrate  a  general  prin- 
ciple. Its  application,  however,  is  usually  unsatisfactory 
and  the  laborious  process  is  unnecessary  when  calculating 
the  heat  loss  for  buildings,  and  Equation  25  is  used  instead. 
Values  of  K  commonly  used  are  obtained  by  experimentation. 
Table  VI  has  been  compiled  from  a  number  of  the  best  refer- 
ences, 
jjjort  «u,  ....  TABLE  VI— Value  of  K 

*77O T~^    '~~'    •   '  ,          •  i  : : '  v 

Materials    .  .,,    ..,  .     ,       ...       ,.         JT_ 

Brick  wall,     %W  plain ; ; .v,,., 37 

Brick  wall,  13"       plain j..     .29 

Brick  wall,  17  y2"  plain 24 

Brick  wall,  22"       plain  21 


64  HEATING  AND   VENTILATION 

Brick  wall,  27"       plain  .................................................................  19 

Brick  wall,  furred  and  plastered,  use  .7  times  non-furred. 

Stone  wall,  use  1.5  times  brick  wall. 

Concrete,   2"  solid   ...........................................................................  78 

Concrete,  3"  solid  ...........................................................................  71 

Concrete,  4"  solid  ...........................................................................  66 

Concrete,   6"  solid  ...........................................................................  56 

Frame  wall   (plaster,  lath,  stud,  clapboard)  ..........  ,  ................  50 

Frame  wall  (plaster,  lath,  stud,  sheating,  clapboard)  .......  28 

Frame  wall  (plaster,  lath,  stud,  sheating-,  paper,  clap- 

board) .........................................................................................  23 

Windows,  single  glass,  full  sash  area  ....................................   1.00 

Plate  glass,  same  as  single  window  glass. 

Windows,  double  glass,  full  sash  area  ...................................  50 

Skylig-ht,  single  glass,  full  sash  area  ....................................   1.10 

Skylight,  double  glass,  full  sash  area  .....................................  60 

Wooden  door,   1"    ............................................................................  40 

Wooden  door,   2"  .............................................................................  36 

Hollow  tile,  2",  y»"  plaster,  both  sides  .....................................  41 

Hollow  tile,  4",   %"  plaster,  both  sides  .....................................  33 

Hollow  tile,  6",   y2"  plaster,  both  sides  .....................................  28 

Solid  plaster  partition,  2"  ......................  .......................................  60 

Solid  plaster  partition,  3"  .............................................................  50 

Concrete  floor  on  brick  arch  .....................................................  20 

Fireproof  construction  as  flooring  ...........................................  10 

Fireproof  construction  as  ceiling  .............  ................................  14 

Single  wood  floor  on  brick  arch  ...............................................  15 

Double  wood  floor,  plaster  beneath  .........................................  15 

Wooden  beams  planked  over,  as  flooring  ...............................  17 

Wooden  beams  planked  over,  as  ceiling  .................................  35 

Lath  and  plaster  ceiling,  no  floor  above  .................................  62 

Lath  and  plaster  ceiling,  floor  above  .......................................  25 

Steel  ceiling,  with  floor  above  ...................................................  35 

Single   %"  floor,  no  plaster  beneath  ........  .  ................................  45 

Single   %,"  floor,  plaster  beneath  ...............................................  26 

APPLICATION.  —  With  zero  outside  temperature  the  heat 
losses  through  the  exposed  glass  and  wall  surfaces  Of  the 
Dining  Room  (Fig.  18),  assuming  good  fran 


glassl  .^...,aa..X...U.4. 
With  —  10°  outside 
2097  =  4657  B.  t.  u.  ;..  nififq  "£2  M&vr 


HEAT   LOSSES   FROM   BUILDINGS 


65 


Most  of  the  values  in  Tab}e  VI  have  been  reduced  to 
chart  form  (Fig-.  15)  where  the  resulting-  values  are  the  total 
B.  t.  u.  transmitted  through  1  square  foot  of  the  surface  per 
hour. 


Fig.   15. 

APPLICATION  1. — Assume  the  outside  temperature  — 10°, 
still  air,  inside  temperature  70°  and  south  exposure.  What 
is  the  heat  loss  from  a  square  foot  of  13-inch  brick  wall; 


66  HEATING  AND  VENTILATION 

also,  from  a  square  foot  of  single  glass  window?  Beginning 
at  the  right  of  the  chart  at  — 10°  outside  temperature,  trace 
to  the  left  to  the  0  wind  velocity,  then  up  the  ordinate  to  the 
13-inch  wall,  then  to  the  left  to  the  line  indicating  70°  in- 
side temperature,  then  down  to  the  south  exposure,  then  to 
the  left  showing  24  B.  t.  u.  transmitted  per  square  foot  per 
hour.  For  the  glass,  trace  from  — 10°  to  the  0  wind  velocity, 
then  up  to  the  single  window,  then  to  the  left  to  the  inside 
temperature,  70°,  then  down  to  south  exposure,  then  to  the 
left  showing  80  B.  t.  u.  per  square  foot  per  hour.  Checking 
this  with  the  table  for  a  13-inch  brick  wall  we  have,  .29  X 
80  =  23.2  B.  t.  u.  For  glass,  1  X  80  =  80.  The  effect  of  the 
wind  upon  the  heat  loss  is  very  marked.  Locations  subjected 
to  high  winds  should  have  extra  allowances.  For  example, 
take  the  13-inch  brick  wall  just  mentioned.  Assume  the 
wind  to  be  30  miles  an  hour.  By  the  same  process  as  before 
we  find  for  a  south  exposure,  33  B.  t.  u.  loss  as  compared 
with  24  at  zero  wind  velocity. 

APPLICATION  2. — Assume  the  outside  temperature  — 10°, 
wind  velocity  12  miles  per  hour,  inside  temperature  7-0°  and 
north  exposure.  What  is  the  heat  loss  from  a  square  foot 
of  13-inch  brick  wall;  also,  from  a  square  foot  of  single 
glass  window?  Trace  as  before  and  find  31  B.  t.  u.  for  the 
wall  and  105  B.  t.  u.  for  the  glass.  This  is  an  increase  of 
approximately  30  per  cent,  over  Application  1,  due  to  ex- 
posure and  wind  velocity. 

APPLICATION  3. — Assume  the  attic  temperature  20°,  zero 
wind  velocity,  south  exposure,  room  temperature  70°,  lath 
and  plaster  ceiling  with  no  floor  above.  What  is  the  heat 
loss  through  a  square  foot  of  ceiling  per  hour?  Trace  from 
20°  outside  temperature  and  find  32  B.  t.  u.  Checking  this 
with  the  table,  .62  X  50  =  31  B.  t.  u. 

APPLICATION  4. — Work  out  Application  3  for  a  steel  ceiling 
with  floor  above  and  check  with  the  table  value. 

APPLICATION  5. — Assume  a  4-inch  concrete  floor  laid  on 
the  ground,  with  a  ground  temperature  of  40°  and  an  air 
temperature  at  the  floor  line  of  65°.  What  is  the  heat  loss 
through  a  square  foot  of  the  floor  per  hour?  Trace  from 
40°  outside  temperature  to  zero  wind  velocity,  down  to 
4-inch  solid  concrete,  to  the  left  to  65°  temperature,  down 


HEAT  LOSSES   FROM   BUILDINGS  67 

to   south   exposure  and  to   the  left  to   17   B.   t.   u.     Check  by 
Table  VI. 

APPLICATION  6. — Assume  a  6-inch  concrete  floor  on  ground 
with  a  ground  temperature  of  50°  and  an  air  temperature  at 
the  floor  line  of  65°.  What  is  the  loss  through  a  square  foot 
of  the  floor  per  hour?  Trace  from  50°  outside  temperature  to 
zero  wind  velocity  (extended),  down  to  6-inch  solid  concrete 
(extended),  to  the  left  to  65°  temperature,  down  to  south 
exposure  and  to  the  left  to  9  B.  t.  u.  Check  by  Table  VI. 

37.  Loss  of  Heat  by  Air  Leakage: — Buildings  are  sub- 
ject to  air  leakage  through  walls,  floors,  ceilings  and  win- 
dow and  door  clearances.  No  effort  is  made  to  estimate  the 
leakage  through  walls.  In  the  best  type  of  windows,  metal 
weather  strips  or  other  insulations  are  used.  Most  of  the 
estimates  of  building  heat  losses,  however,  have  to  do  with 
ordinary  window  construction,  the  quality  of  the  workman- 
ship of  which  is  frequently  very  poor.  Experiments  made 
by  H.  W.  Whitten,  R.  C.  March,  S.  F.  Voohees  and  H.  C. 
Meyer  (Trans.  A.  S.  H.  &  V.  E.,  Vols.  15  and  22;  also,  Jour. 
A.  S.  H.  &  V.  E.,  Jan.  1916)  to  determine  the  amount  of  leak- 
age around  windows  and  doors,  were  very  successful  in  the 
specific  cases.  The  application  of  the  conclusions  to  general 
rules,  however,  is  open  to  much  guess  work,  since  a  well 
fitted  window  has  approximately  &  -inch  clearance,  while  a 
loosely  fitted  window  may  have  as  much  as  332-inch.  In  the 
tests  it  was  shown  also  that  in  any  given  window  clearance 
the  leakage  varied  greatly  as  the  outside  air  velocity  varied. 
For  illustration,  with  a  clearance  of  ^-inch  the  leakage  in- 
creased 25  per  cent,  per  mile  increase  of  wind  velocity;  or  for 
a  four  mile  increase  in  wind  velocity  the  leakage  loss  In- 
creased 100  per  cent.  With  such  variations  as  this  the  heat 
loss  allowance  for  the  average  window  leakage  is  a  question. 
Regardless  of  the  uncertainty  in  "this  part  of  the  work,  it  is 
interesting  to  make  the  best  approximation  possible  and  use 
this  in  estimating  the  heat  loss  from  the  building. 

Some  of  the  approximate  values  determined  by  the  tests 
were: 

(1)  Average  wind  velocity  in  localities  where 

heating  is  important,  miles  per  hr 13 

(2)  Averag'e   sash   clearance,    in tV 


68  H  MATING    AND   VKNTI  LATlnX 

(3)  Air  pressure  equal  to  a  15-mile  wind  against 

a  window  having-  i^-in.  clearance  will  force 
146  to  185  cu.  ft.  of  air  through  each  lineal 
ft.  of  window  clearance  per  hr.  R.  P.  Bol- 
ton  recommends  90  cu.  ft.  Harding  and 
Willard  use  60  cu.  ft. 

(4)  Metal  weather  strips,  etc.,  reduce  the  leakage 

as  low  as  1-5  to  1-9  of  that  found  in  the 
average  wood  frame  window. 

(5)  The   lineal   perimeter  of   the   average   window 

is  numerically  approximately  equal  to  the 
window  area  in  sq.  ft.,  —  G. 

From  these  an  estimate  may  be  made  for  cubic  leakage 
losses  through  the  average  window  per  hour. 

APPLICATION  1. — What  is  the  window  leakage  loss  from 
the  Living  Room,  Fig.  18?  With  a  window  perimeter  =  G, 
a  15  mile  wind  and  a  iV, -in.  clearance  we  have  (assuming1 
100  cu.  ft.  per  hr.  per  lineal  ft.  of  perimeter),  42  X  100  = 
4200  cu.  ft.  of  air  per  hr.  Since  the  room  is  13' x  15' x  10'  = 
1950  cu.  ft.  this  leakage  would  amount  to  4200  -=-  1950  =  2.15 
room  volumes  per  hr. 

APPLICATION  2. — What  is  the  leakage  loss  from 

(a)  Dining-  room?  —  3200  cu.  ft.  hr.  =  1.52   room  volumes 

(b)  Study?  =  4800  cu.  ft.  hr.  =  2.53   room  volumes 

(c)  Kitchen?  G  only         —  3200  cu.  ft.  hr.  rz  2.32   room  volumes 

(d)  Kitchen?  G   +   door   =:  5000  cu.  ft.  hr.  =  3.62  room  volumes 
Professor  Carpenter  in  his  heat  loss  equation  makes  al- 
lowance   for    leakage    losses    by    using    the    factors    n    C   for 
leakage  air,  in  the  term  .02  n  C,  where  n  •=.  number  of  room 
volumes  and   C    =    volume   of   the   room   in   cubic  feet.      The 
use  of  the  term  .02  n  C  is  very  common  practice  among  heat- 
ing  engineers.      The   constant   .02   is   determined   as   follows: 
The  specific  heat  of  air  at  32°    is  .238;   then   the   number  of 
pounds  of  air  heated  from  32°  to  33°  by  1  B.  t.  u.  is  1  ~  .238  = 
4.2.      If    the    weight    of    a    cubic    foot    of    air    at    32°    is    .0807 
pounds,  we  have  4.2  -r-  .0807  =  52  cubic  feet  of  air  heated  by 
1  B.   t.  u.     Since  most  of  the  heating  is  done  at  an  average 
temperature  of  70°  the  volume  of  air  heated  from  69°  to  70° 
by  1  B.  t.  u.  is  52   X    530  4-   492   =   56  cubic  feet  (See  absolute 
temperature,  Art.  4).     It  is  evident  that  some  approximation 
must  here  be  made.     No  exact  value  can   be  taken  because 


HEAT   LOSSES  FROM   BUILDINGS  69 

of  the  great  range  of  temperature  change  of  the  air,  but  55 
is  probably  the  best  average.     The  difficulty  of  handling  the 

1 

equation  with  the  constant has  led  to  the  simple  form  .02. 

55 
(See  last  column  Table  13,  Appendix). 

38.  Exposure  and  Other  Allowances: — Air  at  high  veloc- 
ity   passing   over   the   surface    of   any   radiating   material    is 
more   effective    in   removing  heat   than    air   at   low   velocity. 
The  north,  northwest  and  northeast  in  most  sections  of  the 
country  are  subject  to  the  highest  winds  and  have  the  least 
benefit  from  the  sun,  and  are  therefore  counted  the  cold  por- 
tions   of    the    building.       In    estimating    heat    loss    a    good 
way  is  to  figure  each  room  as  if  it  were  a  south  room    (as- 
sumed to  need  no  additions  for  exposure)   and  add  a  certain 
percentage  of  this  loss  for  exposure  to  fit  the  real  location 
of    the    room.      The    exact    amount    to    add    in    each    case    is 
largely   a  matter   of   the  judgment   of   the   designer,   who   of 
course  is  supposed  to  know  the  direction  of  the  heavy  winds 
and  the  protection  that  is  afforded  by  surrounding  buildings. 
Values  covering  American  practice  vary  between  the  limits 
given  in  Table  VII. 

TABLE  VII. — Exposure. 

North,   northeast  and  northwest  rooms  heav- 
ily exposed  10-25  per  cent. 

East  or  west  rooms  moderately  exposed 5-15  per  cent. 

Rooms  heated  only  periodically- 20-40  per  cent. 

Heat  interrupted  daily  but  rooms  kept  closed..        10  per  cent. 
Heat  interrupted  daily  but  rooms  kept  open....       25  per  cent. 

Heat  off  for  long  periods  50  per  cent. 

Rooms  12  to  I4y2  feet  from  floor  to  ceiling 3  per  cent. 

Rooms  14^  to  18  feet  from  floor  to  ceiling 6  per  cent. 

Rooms  18  feet  and  above  from  floor  to  ceiling       10  per  cent. 

39.  Calculation  of  the  Heat  Losses — Rule: — Estimate  for 
all   rooms   to  be  heated,   the   number  of   square   feet  respec- 
tively of  exposed  glass  surface  (full  sash  area),  exposed  wall 
surface  (gross  wall  minus  glass),  exposed  doors,  floors  above 
unheated  or  partially  heated  spaces,  ceilings  immediately  be- 
low attic  spaces,  and  partition  walls  between  heated  and  un- 
heated spaces.     With  these  values  and  by  the  use  of  Table 
VI,  multiply  each  surface  area  by  its  respective  value  of  K  and  by 
the    temperature    difference    between    the    two    air   envelopes    on    the 


70  HEATING  AND  VENTILATION 

sides.  To  the  sum  of  these  products  add  the  amount  .02  times  the 
cubic  feet  of  air  change  per  hour  times  the  temperature  difference 
between  the  inside  and  outside  air,  and  this  will  represent  the  heat 
loss  for  a  southern  exposure.  For  other  exposures  add  amount 
allowed  for  losses  due  to  location  from  Table  VII. 

APPLICATION  1. — Referring  to  Fig-.  18,  the  Living  Room 
will  have  a  heat  loss  on  a  zero  day  -as  follows:  glass, 
1x42x70  =  2940  B.  t.  u.;  wall,  .23x263x70  =  4234.30  B.  t. 
u.;  floor  (assuming  40°  in  this  part  of  basement),  45  x  195  x 
30  =  2632.50  B.  t.  u.;  and  air  change  (See  Table  VIII), 
.02x2x1950x70  =  5460  B.  t.  u.  Total  15267  B.  t.  u.  Since 
this  is  a  south  room  there  is  no  allowance  for  exposure. 

The  above  rule  may  be  stated  in  equation  form.  Let 
H  =  B.  t.  u.  heat  loss  from  room  per  hour.  With  areas  in 
square  feet,  let  O  =  exposed  glass,  W  =  exposed  wall  minus 
glass,  D  —  exposed  doors,  F  =  floor  or  ceiling  separating 
warm  room  from  unheated  space,  etc.  Also  let  tx  — 
{f  —  to)  —  difference  between  room  temperature  and  outside 
temperature;  ty  =  (t'  —  t")  =  difference  between  room  tem- 
perature and  temperature  of  the  unheated  space;  K,  K'  and 
K"  =  coefficients  of  heat  transmission;  Q  —  nC  in  Arts.  37 
and  40  =  cubic  feet  of  air  change  per  hour,  and  a  —  per- 
centage allowed  for  exposure.  Then 

H  =   (KGtx  +  K'Wt*  +  K"  Ft»  +  Etc.  +  .02  Qt*)   (1  +  a)    (26) 

APPLICATION  2. — With  same  data  as  in  previous  application 
H  =    (1x42x70   +   .23x263x70   +   .45x195x30   + 
.02x2x1950x70)    (1   +   0)    =   15267  B.  t.  u. 

Good  judgment  is  necessary  in  selecting  the  proper  out- 
side temperature,  to,  for  any  locality  (See  Art.  63).  Room 
temperatures  for  heated  rooms,  t',  may  be  taken  from  Table 
IX,  and  temperatures  for  unheated  rooms  and  spaces  from 
Table  X. 

Certain  credits  tending  to  reduce  H  are  frequently  made 
to  the  heat  loss  calculation  by  allowing  for  the  heat  dissi- 
pated from  lights,  persons,  etc.,  within  the  room  (See  Art.  44). 

40.  Short  Rules  for  Estimating  Heat  Loss: — The  method 
of  estimating  heat  losses  outlined  in  Art.  39  can  be  recom- 
mended for  any  heat  loss  calculations.  Engineers  of  experi- 
ence, however,  occasionally  develop  modified  forms  for  their 
own  use,  based  upon  the  method  shown  in  Art.  39  and  suited 
to  average  building  conditions.  These  short  cut  methods 


HEAT  LOSSES  PROM  BUILDINGS 


71 


should    be    used    with    caution    by    persons    not    thoroughly 
acquainted  with  their  development. 

CARPENTERS'  RULE. — According-  to  Prof.  R.  C.  Carpenter 
the  quality  of  building  construction  and  the  corresponding 
heat  losses  from  these  buildings  are  so  varied  and  uncertain 
that  elaborate  methods  of  figuring  heat  losses  are  unneces- 
sary. He  recommends  K  =  .25  for  any  ordinary  wall  sur- 
face and  G  —  1  for  any  glass  surface.  Ceiling  and  floor  sur- 
faces, where  it  is  thought  necessary  to  consider  them,  may 
be  reduced  to  equivalent  wall  surfaces.  The  rule  therefore 
becomes  a  simple  modification  of  Equation  26,  where  tx  = 
t'  —  to. 

H  =    (O  +  .25  W  +  .02  nC)   (f  —  to)   +  exposure       (27) 


TABLE  VIII— Values  of  n 


Residence  heating:  halls  and  bath  rooms,  3;  living  rooms  and 
rooms  on  the  first  floor,  2;  sleeping  rooms  and  rooms  on 
second  floor,  1. 


Offices  and  stores:  first  floor, 

2  to  3; 
second  floor,  iy2  to  2. 

Churches  and  public  assembly 
rooms,   %   to  2. 

Large  rooms  with  small  ex- 
posure, ~y2  to  i. 


The  author  would  suggest 
that  frame  construction, 
large  window  areas  and 
relatively  small  volumes 
tend  toward  the  larger  val- 
ues of  n;  conversely,  brick 
construction,  small  window 
areas  and  relatively  large 
volumes  tend  toward  the 
smaller  values  of  n. 


With  Equation  27,  Table  VIII  should  be  used  and  the 
following  wall  equivalents  may  be  employed  with  good  effect: 

Doors  not  protected  by  storm  doors  or  vestibule,  with  or 
without  small  amount  of  glass  —  200  per  cent,  of  equal  wall 
area. 

Floors  over  unheated  closed  spaces  =   same  as  wall. 

Floors  over  partially  heated  closed  spaces  =  50  per  cent, 
of  equal  wall  area. 

Ceilings  below  unheated  closed  spaces,  no  floors  above  — 
200  per  cent,  of  equal  wall  area. 

Ceilings  below  unheated  closed  spaces,  floors  above  —  50 
per  cent,  of  equal  wall  area. 


72  HEATING  AND   VENTILATION 

APPLICATION  3. — With  the  same  room  and  data  as  in  Ap- 
plication 1. 

H  —    [42    +   .25    X    (263    +   .5x195)    +   .02x2x1950]    70    = 
14707  B.  t.  u. 

HARDING  AND  WILLARD'S  RULE. — This  is  a  modification  of 
Carpenter's  Rule  with  the  term  .02  nC  replaced  by  a  leakage 
factor  in  terms  of  the  window  and  door  perimeter,  P.  Use 
window  and  door  perimeter  on  that  outside  wall  having  the 
greatest  amount  of  window  and  door  surface. 

H  =    ((!   +   .25  W  +   CP)   (f  —  to)   +   exposure          (28) 

Where  the  value  of  C  is  taken  for 

Good  construction — a5-in.  sash   clearance....     1.2 

Poor  construction — i'g-in-  sash  clearance 2.4 

Weather  strippe'd  sash  0.15 

APPLICATION  4. — With  the  same  room  and  data  as  in  Ap- 
plication 3,  assuming  both  windows  to  'be  affected  simul- 
taneously by  the  air  pressure 

H,  Good  Const.   =    [42   +   -25   (263  +  .5  x  195)  +  1.2  x  42] 
70   =   12747  B.  t.  u. 

//,  Poor  Const.  =    [42   +  .25   (263   +  .5x195)    +   2.4x42] 
70  =   16303  B.  t.  u. 

One  of  the  difficulties  in  the  application  of  Equation  28 
is  to  determine  the  character  of  the  sash  clearance.  In  all 
probability  the  average  value  C  will  approach  2.4  rather 
than  1.2. 

41.  Loss  of  Heat  by  Ventilation: — Heating  and  Ven- 
tilating systems  should  have  special  provisions  made  for 
supplying  fresh  outdoor  air  for  the  inhabitants  of  the  rooms 
and  exhausting  a  corresponding  amount  of  foul  air.  The 
exhausted  air  is  usually  warm  air  and  as  it  leaves  the  rooms 
carries  a  certain  amount  of  heat  with  it.  This  is  a  direct 
loss  and  should  be  taken  into  account. 

Since  the  loss  by  leakage  is  the  same  for  any  building 
regardless  of  the  heating  system  employed,  it  is  accounted 
for  in  the  ordinary  heat  loss  equation,  but  losses  through 
ventilating  systems  must  be  considered  in  excess  of  this 
amount.  Let  Qr  =  cubic  feet  of  fresh  air  supplied  through 
the  ventilating  system  per  hour,  /'  —  to  =  drop  in  tempera- 
ture from  the  inside  to  the  outside  air;  then  the  heat  lost  by 
exhausting  the  air  is 

0,.    (f  —  to) 

(29) 

55 


HEAT   LOSSES  FROM   BUILDINGS  73 

42.  Combined  Heat  Loss,  //'    =    (H  •+   Hv)  : — In  buildings 
where  ventilation  is  provided,  the  total  heat  loss  is  that  lost 
by  conduction  and  radiation,  H,  +  that  lost  by  ventilation,  Hv 
(See  also  Art.  50). 

Qv   (f  —  to) 

H'   =   H   +   -  (30) 

55 

Rule. — To  find  the  total  heat  Jost  from  any  building,  add  to  the 
heat  loss  calculated  by  equation,  the  amount  found  by  multiplying  the 
number  of  cubic  feet  of  ventilating  air  exhausted  from,  the  building  per 
hour  by  one-fifty-fifth  of  the  difference  between  the  inside  and  outside 
temperatures. 

43.  Temperatures  to  be  Considered: — In  designing  heat- 
ing systems  the  following  temperatures  may  be  used: 

TABLE  IX — Values  of  «'. 

Living  rooms,  school  rooms,  offices,  auditoriums,  lecture 

halls  and  general  laboratories 70 

Play  rooms,  gymnasiums,  manual  training  rooms,  locker 

rooms  and  toilet  rooms  65 

Bath    rooms    80 

Hospitals,  sick  rooms  and  treatment  rooms 75 

Greenhouses  70-80 

Shops  and  manufacturing  plants,  hard  labor 60 

Shops  and  manufacturing  plants,  light  labor 65 

Paint  and  finishing  rooms  80 

Outside  temperatures,  to,  should  be  estimated  from  the 
lowest  temperature  recorded  by  the  weather  bureau  for  that 
locality,  during  the  preceding  ten  years.  This  will  range 
from  10°  in  the  southern  to  — 30°  for  the  northern  sections 
of  the  country.  The  most  extreme  low  temperatures  are  of 
such  short  duration  that  one  is  not  justified  in  designing  for 
these.  Usually  ten  degrees  above  the  lowest  recorded  tem- 
perature is  used  (See  Art.  63). 

The  temperatures  of  rooms  not  specifically  heated  may 
be  taken: 

TABLE  X — Values  of  to  when  applied  to  a  room 

Cellars  and  rooms  kept  closed  32 

Rooms  often  in  communication  with  the  outside  air,  such 

as  passages,  entrance  halls,  vestibules,  etc 23 


74  HEATING  AND  VENTILATION 

Attic  rooms  immediately  beneath  metal  or  slate  roof 14 

Attic  rooms  immediately  beneath  tile,  cement,  or  tar  and 

gravel  roof  23 

44.  Heat  Given  Off  from  Lights  and  from  Persons  With- 
in the  Room: — As  a  credit  to  the  heating  system,  some  heat- 
ing engineers  take  account  of  the  heat  radiated  from  lights 
and  persons  within  the  rooms.  The  following  values  are 
collected  from  various  authorities  and  may  be  considered 
fair  averages: 

TABLE   XI. 

Gas,  ordinary    split  burner,  B.  t.  u.  per  candle  power  hr.     300 
Gas,  Argand  "  "  200 

Gas,  Auer  "  31 

Petroleum  "  160 

Alcohol,   incandescent    "  40 

Electric,  incandes'nt  carbon  filament  "  "  14 

Electric,  metal  filament     '  4 

Electric,  arc  5 

According  to  Pettenkofer,  the  mean  amount  of  heat 
given  off  per  person  per  hour  is  400  heat  units  for  adults 
and  200  for  children. 


45.  Performance  to  Guarantee  Heating;  Capacity: — Some 
contracts  guarantee  that  the  heating  system  (steam  or  hot 
water  radiation)  will  maintain  the  interior  temperature  of 
the  building  at  70°  when  the  outside  temperature  is  zero  or 
some  value  below.  It  is  frequently  necessary  to  make  tests 
to  prove  the  fulfillment  of  such  guarantees  when  the  out- 
side temperature  is  above  that  stated  in  the  guarantee.  It 
is  evident  that  the  inside  temperature  of  the  room  while 
under  test  will  then  be  in  excess  of  70°.  To  maintain  the 
temperature  that  will  give  an  equivalent  heating  value  to 
the  guarantee,  is  the  object  of  the  test.  Tests  of  this  char- 
acter are  never  as  satisfactory  as  when  conducted  under 
guaranteed  conditions,  but  may  be  estimated  with  a  fair  de- 
gree of  accuracy.  A  method  proposed  ~by  William  Kent  in  the 
Engineering  Record,  Aug.  11,  1894  (See  also  M.  E.  Pocket 
Book),  assumes  that  K  is  constant  for  any  given  material 
under  temperature  differences  ordinarily  found  in  practice; 
also,  that  the  heat  lost  from  the  house  equals  the  heat  given 


PERFORMANCE  OF  HEATING  GUARANTEE     75 

up  by  the  radiator.  It  is  found  from  experimental  data  that 
K  is  not  constant  for  varying-  temperature  differences  but 
that  it  may  be  so  considered  without  serious  error. 

Let  R  =  sq.  ft.  of  radiator  surface;  Wb  =  sq.  ft.  of  sur- 
face of  exposed  walls,  windows,  etc.;  ts  =  temperature  inside 
the  radiator;  t'  =  room  temperature  while  under  test;  t  = 
guaranteed  room  temperature;  t'o  =  outside  temperature  at 
time  of  test;  to  =  outside  temperature  specified  on  guaran- 
tee; Kr  —  rate  of  transmission  through  radiator;  Kb  —  aver- 
age rate  of  transmission  through  building  walls.  From  the 
conditions  of  guarantee  Kr  R  (ts  —  t)  =  Kb  Wb  (t  —  to);  c  = 
(Kb  Wb  -H  Kr  R);  t  =  (ts  +  cto)  -T-  (1  +  c)  and  c  =  (ts  —  *)  -r- 
(t  —  to).  Then  from  the  conditions  of  the  test 

t'   =    (ts   +  ct'o)    -T-    (1   +  c)  (31) 

which  gives  the  temperature  of  the  room  under  test  corre- 
sponding to  the  given  values  of  ts  and  to. 

APPLICATION  1. — Suppose  the  heating  system  in  any  de- 
sign is  guaranteed  to  heat  the  interior  of  the  house  to  70° 
at  — 10°  outside  temperature,  when  the  steam  pressure  is 
atmospheric,  and  that  the  test  of  acceptance  is  to  be  run 
when  the  outside  temperature  is  60°.  What  will  be  the 
maintained  inside  temperature,  t',  to  satisfy  this  guarantee? 
From  the  conditions  of  the  guarantee  find  c  —  (212  —  70)  -r- 
[70  —  ( — 10)]  —  1.775.  Then  from  the  conditions  of  the  test 
t'  =  (212  +  1.775  X  60)  4-  (1  +  1.775)  =  115°.  In  this  same 
application  if  the  heating  system  is  guaranteed  to  heat  to 
70°  when  the  outside  temperature  is  0°  we  would  have  t'  = 
(212  +  2.029  X  60)  -^  (1  +  2.029)  =  110°. 

A  second  method,  very  similar  to  the  preceding  and  found 
in  Mechanical  Equipment  of  Buildings,  Vol.  1,  Harding  and 
Willard  also  makes  the  assumption  that  K  is  constant  for 
varying  temperatures.  From  the  two  equations,  (G  + 
.25TF  +  .02  nO)  (t  —  to)  =  Kr  R  (ts  —  t)  and  (G  +  .25  W  + 
.02  nC)  (tf  —  t'0)  —  KrR  (ts  —  t'),  we  have  by  division  (f  — 
t'o)  -f-  (t  —  to)  =  (ts  —  t')  -=-  (ts  —  t)  and 

ts   (t'o  +  t to)  t'o   X    t 

t'  =  (32) 

ts  —  to 

APPLICATION  2. — With  the  same  conditions  of  guarantee 
and  test  as  given  in  Application  1.  t'  =  115°  for  to  =  — 10° 
and  110°  for  to  =  0. 

A  third  method,  by  W.  W.  Macon,  is  shown  in  Table  48, 
Appendix. 


CHAPTER  IV. 


FURNACE    HEATING    AND    VENTILATING. 


PRINCIPLES    OF    DESIGN. 

46.      Furnace    System    Compared    with    Other    Systems: — 

The  plan  of  heating  residences  and  other  small  buildings  by 
furnaces  in  which  the  air  serves  as  a  heat  carrier,  is  com- 
mon in  this  country.  Some  of  the  points  in  favor  of  the  fui  - 
nace  system  are:  low  cost  of  installation,  heating  combined 
with  ventilation,  and  adaptability  to  light  service  and  sud- 
den changes  of  outdoor  temperature.  Compared  with  that 
of  other  heating  systems,  a  first-class  furnace  system  can 
be  installed  for  one-third  to  one-half  the  cost.  In  addition 
to  this,  the  fact  that  ventilation  is  so  easily  obtained  and 
that  the  consumption  of  fuel  may  be  so  nearly  proportioned 
to  the  demands  of  the  weather,  give  this  method  of  heating 
many  advocates.  The  objections  to  the  system  are:  the  diffi- 
culty of  heating  the  windward  side  of  the  house,  circulated 
dust,  and  the  contamination  of  the  air  supply  by  the  fuel 
gases  leaking  through  the  joints  in  the  furnace.  In  a  good 
system  well  installed,  the  only  objection  to  be  seriously  con- 
sidered is  the  difficulty  of  heating  that  part  of  the  house 
subjected  to  the  pressure  of  the  heavy  wind.  The  natural 
draft  from  a  warm  air  furnace  is  not  very  strong  at  best  and 
any  differential  pressure  in  the  various  rooms  will  tend  to 
force  the  air  toward  those  rooms  offering  the  least  resist- 
ance. In  a  properly  designed  furnace  plant,  however,  the 
layout  may  be  so  made  as  to  reduce  this  possible  differential 
to  a  minimum.  The  cost  of  operation  can  be  largely  controlled 
by  the  owner,  consistent  with  his  ideas  of  the  quality  of  the 
ventilation  needed.  Arrangements  may  be  made  to  carry  the 
room  air  back  to  the  furnace  to  be  reheated,  in  which  case 
(fresh  air  cut  off  entirely)  the  cost  of  heating  is  about  the 
same  as  that  of  any  system  of  direct  radiation  having  no 
special  provision  for  ventilation.  Beyond  this,  any  amount 
of  fresh  air  desired  may  be  taken  from  the  outside  and 
mixed  with  the  room  air  for  the  purpose  of  ventilation.  This 


FURNACE   HEATING  77 

requires  the  same  amount  of  room  air  to  be  exhausted  from 
the  house  at  the  room  temperature  and  causes  an  increased 
cost  of  operation,  as  discussed  in  Art.  50. 

47.  Essentials  of  the  Furnace  System: — Fundamentally 
this  installation  must  contain  a  furnace  upon  a  proper  set- 
ting-, a  carefully  desig-necl  and  constructed  system  of  fresh 
air  supply  and  return  ducts,  and  the  warm  air  distributing- 
leaders,  stacks  and  registers.  Fig.  16  shows  a  common 


Fig.  16. 

arrangement  of  these  essentials.  Dampers  in  the  various 
air  lines  in  the  basement  provide  means  whereby  fresh  air 
may  be  taken  from  the  outside  or  recirculated  air  from  the 
rooms  as  desired.  Return  registers  and  ducts  are  placed  in 
the  coldest  sections  of  the  building  (in  some  cases  each 
room)  and  should  lead  by  the  shortest  lines  to  the  furnace. 
48.  Points  to  be  Calculated  in  a  Furnace  Design: — In 
addition  to  the  calculated  heat  loss,  H,  which  may  be  as- 
sumed the  same  for  all  methods  of  heating,  other  points  in 


78  HKATJX';    ,\XD    VKXTILATIOX 

furnace  plant  design  should  be  taken  up  in  the  following- 
order:  find  for  each  room  the  cubic  feet  of  air  needed  as  a 
heat  carrier  and  determine  if  this  amount  of  air  is  sufficient 
for  ventilation;  then  obtain  from  this  the  areas  of  the  net 
heat  registers,  gross  heat  registers,  heat  stacks,  net  vent 
registers,  gross  vent  registers,  vent  stacks,  leader  pipes, 
fresh  air  duct  and  total  grate  area.  From  the  total  grate 
area  select  the  furnace. 

49.  Air    Circulation    in    Furnace    Heating: — The    use    of 
air  in  furnace  heating  may  be  considered  from   two   stand- 
points, each  very  distinct  in  itself.     First,  air  as  a  heat  carrier; 
second,  air  as  a  health  preserver.     The  first  may  or  may  not 
be  fresh  air.     All  that  is  necessary  is  to  provide  enough  air 
to   carry  the  required   amount  of  heat  from   the   furnace   to 
the   rooms,   i.   e.,   that   amount  of  heat  that   will   replace   the 
heat  lost  by  radiation  plus  the  small  amount  that  is  carried 
away   by   leakage.     With   given   temperatures   of  air   at   the 
register  and  in  the  room,  the  volume  of  air   (volume  at  the 
register)  may  be  easily  calculated.     The  second  requires  that 
enough  air  be  sent  to  the  rooms  to   provide  ventilation  for 
the   occupants.      Each   of   these   two   amounts   should   be   de- 
termined  and    the    greater   used    in    estimating    the    sizes    of 
the  registers  and  ducts.     As  previously  stated,  the  cubic  feet 
of  air  per  hour  for  ventilation  may  be  taken  1800  N,  where 
N  is  the  number  of  persons  to  be  provided  for   (See  Art.  21). 

50.  Air   Circulated    per   Hour   and    Total   Heat    Loss: — A 
safe   temperature   t,   of   the   circulating   air   as   it   leaves   the 
heat    register,    is    130°.      This    may    at    times    reach    150°    or 
above,  but  it  is  not  well  to  use  the  higher  values  in  the  de- 
sign calculations.     If  the  room  air  temperature  is  t'   =    70°, 
the    incoming    air    to    the    room    will    drop    in    temperature 
through   60  degrees,  and  since  one  cubic  foot  of  air  can  be 
heated   through   55    degrees   by   one   B.   t.   u.    it   will   give   off 
60   ^   55   =   1.09    (say  1.1)  B.  t.  u. 

Let  Q  =  cubic  feet  of  air  per  hour  as  a  heat  carrier; 
H  =  total  heat  loss  in  B.  t.  u.  per  hour  by  equation;  t  = 
temperature  of  the  air  at  the  register;  and  t'  =  temperature 
of  the  room  air;  then 

55  H 
Q  =  (33) 

t  —  t' 

Rule. — To  find,  the  cubic  feet  of  air  necessary  to  carry  the  heat 
to  the  rooms,  multiply  the  heat  loss  calculated  In/  equation  by  fifty- 


FURNACE   HEATING  79 

five  and  divide  by  the  difference  betivccn  the  register  and  the  room 
temperatures.     For  ordinary  furnace  work  this  becomes 

H 

°=TT 

Now  if  this  air  is  not  specially  exhausted  from  the  build- 
ing but  is  taken  back  to  the  furnace  and  recirculated,  the 
only  loss  of  heat  will  be  H.  Since  air  thus  used  would  soon 
become  unfit  for  the  occupants  to  breathe,  it  is  well  to  ex- 
haust through  ventilating-  flues  a  part  or  all  of  the  air  sent 
from  the  furnace.  This  makes  an  additional  loss  of  heat 
corresponding  to  the  drop  in  temperature  from  70°  to  that 
of  the  outside  air  (See  Arts.  41  and  42).  If  the  temperature 
of  the  outside  air  is  assumed  0°,  — 10°  and  — 15°  respec- 
tively, the  resulting  heat  loss  will  be 

H'o  =  H+1.27  Qf;H'-10  =  H+  1.45  Q?;  H'-LS  =  H  +  1.54  <?„      (34) 

For  illustration,  consider  the  Living  Room  (Fig.  18)  under 
three  conditions  on  a  zero  day:  first,  when  all  the  air  is  re- 
circulated;  second,  when  only  enough  air  is  exhausted  to 
give  fresh  air  for  ventilation;  third,  when  all  the  air  is  ex- 
hausted. Under  the  first  case  the  loss  //  is  15267  B.  t.  u.  per 
hour  and  no  other  loss  is  experienced.  In  the  second  case, 
if  three  people  occupy  the  room  and  each  is  allowed  1800 
cubic  feet  of  fresh  air  per  hour,  the  total  heat  loss  will  be 
15267  +  1.27  X  5400  =  22125  B.  t.  u.  In  the  third  case, 
where  all  the  air  is  exhausted,  15267  +  1.1  =  13879  cubic 
feet  of  fresh  air  per  hour  will  be  raised  from  0°  to  70° 
which  will  increase  the  heat  loss  1.27  X  13879  =  17626 
B.  t.  u.,  making  a  total  loss  of  32893  B.  t.  u.  per  hour.  The 
second  condition  is  that  which  would  be  found  most  satis- 
factory. 

It  is  evident  from  inspection  that  the  cubic  feet  of  air 
necessary  as  a  heat  carrier  will  be  excessive  for  ventilation 
in  the  average  residence  (See  Art.  51),  and  the  designer  need 
not  consider  the  amount  of  air  for  ventilation  in  calculating 
the  sizes  of  the  ducts  and  registers.  However,  this  will  be 
needed  in  an  investigation  of  the  size  of  the  furnace,  the 
amount  of  coal  burned  or  the  cost  of  heating;  the  latter  be- 
ing in  direct  proportion  to  the  respective  total  heat  losses 
(See  Art.  63). 

APPLICATION.— Referring  to  Table  XII,  the  calculated 
amount  of  air  Q,  for  the  various  rooms  of  a  residence  may 
be  found. 


80  HEATING  AND  VENTILATION 

51.  Is  This  Amount  of  Air  Q,  Sufficient  for  Vrentilation  if 
Taken  from  the  Outside? — Assume  the  same  room  as  in  Art. 
50  with  Q   =    13879   cubic  feet.     With  a  room  volume  of  1950 
cubic  feet,  the  air  will  change  7.1  times  per  hour  and,  allow- 
ing 1800  cubic  feet  of  air  per  person,  will  supply  eight  per- 
sons with  good  ventilation  if  fresh  air  is  used.     Stated  as  an 
equation  this  is 

II  H 

N   =   =  approx.  (35) 

1.1    X    1800  2000 

As  a  matter  of  fact,  ventilation  for  half  this  number  will  be 
ample  in  an  ordinary  residence  room  excepting  on  extraor- 
dinary occasions.  Test  ty  for  other  rooms  and  find  that  ducts 
and  registers  designed  sufficiently  large  to  carry  air  for  heating  pur- 
poses are  ample  for  ventilation  in  residences. 

52.  Given    the    Heat    Loss    If    and    the    Volume    of   Air    Q' 
for  Any  Room,  to  Find   t,  the  Temperature  of  the  Air  Enter- 
ing  at   the   Register: — If   for   any   reason    Q   is   not    sufficient 
for  ventilation   (schools,   offices,  auditoriums,   etc.),  more   air 
must  be  sent  to  the  room  and  the  temperature  dropped  cor- 
respondingly to  avoid  overheating  the  room.     Let  Q'  =   total 
volume  of  air  per  hour  (including  extra  air  for  ventilation), 
measured  at  the  register,  then 

55  H 

t   =   70   +   -  (36) 

Q' 

Rule. — When  it  is  necessary  for  ventilating  purposes  to  circulate 
more  air  than  that  calculated  from  the  hetit  loss  equation,  then  the 
temperature  at  the  register  ir.il I  be  found  bu  adding  lo  seventy  de- 
grees the  amount  found  by  multiplying  the  heat  loss  by  fifty-five  and 
dividing  by  the  cubic  feet  of  circulated  air.  This  rule  applies  to 
all  indirect  heating. 

APPLICATION*. — Suppose  it  \vere  necessary  on  a  zero  day 
to  send  18000  cubic  feet  of  fresh  air  to  the  above  room  per 
hour  to  accommodate  ten  people.  The  temperature  of  the  air 
at  the  register  should  be 

55  X  15267 

t  =   70   -\ =   116.6° 

18000 

53.  Net  Heat  Registers: — The  velocity  of  the  air,  T7,  as 
it  leaves  the  heat  register  is  assumed  3  to  4  feet  per  second 
by  different  designers.  The  mean  value  is  recommended  for 
registers  placed  near  the  floor  line.  Where  they  are  placed 


FURNACE   HEATING  81 

above  the  heads  of  the  occupants  of  the  room  (See  Art.  134), 
higher  velocities  may  be  used.  The  general  equation  for  net 
register  area  in  square  inches  is 

H  X  55  X  144 

AT.  //.  R.  —  -  (37) 

(*•—#')  X  v  X  3600 

Rule. — To  find  the  square  inches  of  net  heat  register,  multiply 
the  heat  Joss  calculated  by  equation  by  two  and  two-tenths  and  divide 
by  the  product  of  the  velocity  in  feet  per  second,  times  the  difference 
in  temperature  between  the  register  and  the  room  air. 

Assuming  a  mean  velocity  of  3.5  feet  per  second  for  all 
floors  and  60  degrees  drop  in  temperature  from  the  register 
to  the  room,  Equation  37  becomes 

H  X  55  X  144 

N.  H.  R.   =  =   .01  //  (38) 

60  X  3.5  X  3600 

54.  Net  Vent  and  Return  Registers: — Vent  registers  or 
return  registers  or  both  should  be  put  in  at  every  important 
part  of  the  design,  but  this  is  not  always  done.  In  order 
that  any  room  may  be  heated  properly  it  is  necessary  that 
the  room  air  be  allowed  to  escape  to  permit  the  heated  air 
to  come  in.  This  may  be  done  by  venting  through  doors, 
windows  or  transoms  but  the  ideal  way  is  through  special 
ducts  to  the  attic  or  back  to  the  furnace.  A  tightly  closed 
room  cannot  be  properly  heated  by  a  furnace  (See  Art.  67). 

If  all  the  air  were  to  pass  out  the  vent  or  return  register, 
at  the  same  velocity  as  it  entered  through  the  heat  register, 
the  area  of  the  vent  or  return  register  would  be  to  the  area 
of  the  heat  register  as  the  ratio  of  the  absolute  temperatures 
of  the  leaving  and  entering  air;  that  is,  the  area  of  the  vent 
or  return  register  =  .9  the  area  of  the  heat  register.  Since 
some  of  the  air  leaves  the  room  through  other  openings, 
these  registers  need  not  be  so  large,  say 


,.,,  i 

-V.  *.«.     / 


=   ,007  H  =   .1  N.  H.  R. 


55.  Gross  Register  Area: — The  nominal  size  (catalog 
size)  of  the  register  is  usually  stated  as  the  two  dimensions 
of  the  rectangular  opening  into  which  it  fits.  The  area  of 
this  opening  varies  from  one  and  one-half  to  two  times  the 
net  area.  The  larger  value  is  for  floor  registers  and  is  the 
safer  one  to  follow  unless  the  exact  value  is  known  for  any 


82  HEATING  AND  VENTILATION 

special  make  of  register.  Wall  registers  have  lighter  bars 
and  for  the  same  net  area  have  somewhat  smaller  gross 
area. 

G.  R.   =    (1.5  to  2)  times  the  net  register  (40) 

Round  registers  may  be  had  if  desired.  Register  sizes  may 
be  found  in  Tables  19  and  21,  Appendix. 

56.  Heat  Stacks: — The  vertical  ducts  delivering  air  to 
the  registers  are  called  stacks.  To  install  the  proper 'sized 
stacks  in  any  heating  system  is  very  important.  By  some 
designers  the  cross  sectional  area  is  taken  a  certain  ratio 
to  that  of  the  net  register.  This  has  been  quoted  anywhere 
from  50  to  90  per  cent.  Prof.  Carpenter  suggests  4,  5,  and  6 
feet  per  second  respectively,  as  the  air  velocities  for  stacks 
leading  to  the  first,  second,  and  third  floors.  Mr.  J.  P.  Bird 
(Metal  Worker,  Dec.  16,  1905)  used  280,  400,  and  500  feet  per 
minute,  which  is  approximately  4.5,  6.5,  and  8  feet  per  second 
for  the  respective  floors.  The  cross  sectional  areas  of  the 
heat  stack,  with  velocities  4,  5.5,  and  7  feet  per  second,  are 

H  X  55  X  144  .0091  H  1st  floor 

H.  S.  =  -  =  .0066  H  2nd  floor      (41> 

60  X   (4,  5.5,  or  7)  X  3600          .0052  H  3rd  floor 

Rule. — See  rule  under  net  heat  registers  with  changed  value 
for  velocity. 

The  theoretical  air  velocity  in  the  stack  is  based  upon 
the  equation  v  =  V2#/*,  where  7t  =  (effective  height  of 
stack)  X  (t  —  «')  -f-  (460  +  t');  v  is  in  feet  per  second;  t  is 
the  temperature  of  the  stack  air;  and  t'  is  the  temperature 
of  the  room  air.  The  calculated  velocities  from  this  equa- 
tion are  much  higher  than  those  that  obtain  in  practice  be- 
cause of  the  retarding  influence  of  the  shape  of  the  cross 
section,  the  friction  of  the  sides,  and  the  abrupt  turns  in  the 
stack. 

Assuming  the  net  register  to  be  figured  at  3.5  feet  per 
second,  the  quotations  by  Carpenter  and  Bird  give  heat 
stack  areas  for  the  first  floor,  88  and  75  per  cent.;  second  floor, 
70  and  53  per  cent.;  and  third  floor,  58  and  42  per  cent,  of  the 
net  register.  Good  sized  stacks  are  always  advisable  (See 
Art.  71,  but  because  of  the  limited  space  between  the  stud- 
ding it  becomes  necessary  at  times  to  put  in  a  stack  that  is 
too  small  or  to  increase  the  thickness  of  the  wall,  a  thing 
which  the  architect  is  occasionally  unwilling  to  do.  From 


FURNACE  HEATING  83 

the  above  figures,  checked  by  existing  plants  that  are  work- 
ing satisfactorily,  the  following  approximate  figures  will 
give  good  results. 

.008  H  =  .SN.  H.  R.,  first  floor 

//.  8.    —   .006  H  =  .6  N.  H.  R.,  second  floor  (42) 

.005  H  =  .5  N.  H.  R.,  third  floor 

57.      Vent    and    Return    Stacks: — Estimated    in    the    same 
manner  as  the  N.  V.  R.,  these  may  be  made 


V.  S.  ) 

>    =  .1  H.  S. 
R.  S.  j 


(43) 


As  a  matter  of  practice  it  will  be  satisfactory  to  make  these 
stacks  in  average  residence  rooms,  one  or  more  tin  stacks, 
full  opening  between  studs;  the  total  cross  sectional  area 
approximating  the  equation. 

58.  Leader  Pipes: — Since  all  the  air  that  passes  through 
the  stacks  must  pass  through  the  leader  pipes,  it  might  be 
assumed  that  the  cross  sectional  areas  of  the  two  would  be 
equal.     There  are  two  reasons  why  this  should  not  be.     Be- 
cause  of  their  vertical   position,   stacks  offer  less   frictional 
resistance,  area  for  area,  than  leader  pipes  with  their  small 
pitch   and   abrupt   turns.     Also   there    is   some   drop   in   tem- 
perature as  the  air  passes  through  the  leader  pipes,   conse- 
quently   the    volume    entering    from    the    furnace    is    greater 
than  that  going  up   the  stack.     Considering  these   points   it 
would  be  well  to  make  the  area  of  the  leaders 

(.008  to  .009)  H  =   (.8  to  .9)  N.  H.  R.,  first  floor 

L.P.  =  (.006  to  .007)  H  =   (.6  to  .7)  N.  H.  R.,  second  floor     (44) 

(.005  to  .006)  H  =   (.5  to  .6)  N.  H.  R.,  third  floor 

the  exact  figures  to  depend  upon  the  length  and  inclination 
of  the  leader  (See  Art.  69). 

59.  Fresh  Air  Duct: — The  area  of  the  fresh  air  duct  is 
determined  largely  by  experience  as  in  the  case  of  the  vent 
and  return  lines.     It  is  generally  taken 

F.  A.  D.  =  .8  times  the  total  area  of  the  leaders  (45) 
Assume  the  average  velocity  of  the  air  in  the  leaders  to  be 
6  feet  per  second  and  the  area  of  the  fresh  air  duct  to  be  as 
stated,  then  if  the  air  in  each  were  of  the  same  temperature, 
the  velocity  in  the  fresh  air  duct  would  be  6  -^  .8  =  7.5  feet 
per  second;  but  since  the  temperatures  are  different,  the 
velocities  will  be  in  proportion  to  the  absolute  temperatures. 
In  this  case— 0°,  .78  X  7.5  =  5.8;  at  25°,  .82  X  7.5  =  6.2;  and 
at  50°,  .88  X  7.5  =  6.6  feet  per  second.  It  is  seen  by  this 
that  although  the  area  of  the  fresh  air  duct  is  contracted  to 


84  HEATING  AND  VENTILATION 

80  per  cent,  of  that  of  the  leaders,  the  velocity  is  below  that 
of  the  leaders.  It  is  always  well  to  have  a  fresh  air  duct 
that  is  simple  in  cross  sectional  area  and  free  from  obstruc- 
tions and  sharp  turns. 

ttO.  Grate  Area* — The  grate  area  of  a  furnace  is  esti- 
mated from  the  total  heat  loss,  assuming  the  quality  of  the 
coal,  the  efficiency  of  the  furnace,  and  the  pounds  of  coal 
burned  per  hour  per  square  foot  of  grate.  The  heat  value 
of  the  coal  will  be  between  11000  and  14000  B.  t.  u.  per 
pound  as  shown  in  Table  15,  Appendix.  The  efficiency  of  the 
average  furnace  is  approximately  60  per  cent.,  and  the  coal 
burned  per  square  foot  of  grate  per  hour  ranges  from  3  to  7 
pounds  (See  Art.  61).  Furnaces  are  charged  from  two  to 
four  times  each  twenty-four  hours.  This  requires  a  good 
sized  fire  pot  and  a  possibility  of  banking  the  fires.  To 
allow  5  pounds  per  square  foot  of  grate  per  hour  is  as  good 
an  average  as  can  be  made  for  most  coals  in  furnace  work. 
Let  H'  =  total  heat  loss  from  building  including  ventilation 
loss,  E  =  efficiency  of  furnace,  f  =  value  of  coal  in  B.  t.  u. 
per  pound,  and  p  =  pounds  of  coal  burned  per  square  foot 
of  grate  per  hour.  The  equation  for  the  square  inches  of 
grate  area  is 

H'  X  144 

G.  A.  =  -  (46) 

E  X  f  X  P 

Rule. — To  find  the  square  inches  of  grate  area  for  any  furnace, 
multiply  the  total  heat  loss  from  the  building  per  hour  l)y  one  hun- 
dred and  forty-four  and  divide  l)y  the  quantity  found  by  multiplying 
the  total  pounds  of  coal  burned  per  hour  by  the  heat  value  of  the 
coal  and  the  efficiency  of  the  furnace. 

APPLICATION. — In  the  typical  residence  (Art.  62),  IT  on  a 
zero  day  is  110574  B.  t.  u.  per  hour.  This  will  require  101000 
cubic  feet  of  air  per  hour  as  a  heat  carrier.  Assuming  as  a 
maximum  that  ten  people  will  be  in  the  house  and  that"  they 
will  need  18000  cubic  feet  of  fresh  air  per  hour  for  ventila- 
tion, this  air  will  carry  away  approximately  22900  B.  t.  u. 
per  hour,  making  a  total  heat  loss  from  the  building  of 
133474  B.  t.  u.  per  hour.  If  the  furnace  is  60  per  cent,  effi- 
cient and  burns  5  pounds  of  14000  B.  t.  u.  coal  per  hour  per 
square  foot  of  grate,  we  have 

133474  X  144 

O.  A.  —  : —  458  square  inches  =  24  inches 

.60  X  14000  X  5 

diameter.     With  coal  at  13000  B.   t.   u.  per  pound,   the  grate 


FURNACE   HEATING  85 

would  be  493  square  inches  or  25  inches  diameter;  at  12000, 
534  square  inches  or  26  inches  diameter;  at  11000,  582  square 
inches  or  27  inches  diameter. 

In  any  specific  case  it  would  be  wise  to  estimate  the 
grate  size  from  the  heat  value  of  the  poorest  grade  of  coal 
likely  to  be  used.  In  this  case  the  estimated  diameter  of  the 
grate  varied  three  inches  between  coal  samples  nominally 
rated  at  14000  and  11000.  This  variation  is  too  great  to  be 
overlooked  in  the  selection  of  furnaces.  With  the  assump- 
tion made  above,  the  equation  becomes  G.  A.  rz  .0035  H'  for 
the  better  grades  of  coal,  and  G.  A.  —  .0044  //'  for  the  poorer 
grades.  For  the  average  coals  a  fairly  safe  value  is 

G.  A.  square  inches   =   .004  //'  (47) 

61.  Heating  Surface: — The  right  amount  of  heating-  sur- 
face to  require  in  any  furnace  is  rather  an  indefinite  quan- 
tity. Manufacturers  differ  upon  this  point.  Some  standards 
may  soon  be  expected  but  at  present  only  rough  approx- 
imations can  be  stated.  One  of  the  chief  difficulties  is  in 
determining  what  is,  or  what  is  not,  heating  surface.  Some 
quotations  no  doubt  include  surfaces  that  are  very  ineffi- 
cient. In  estimating-,  only  prime  heating-  surface  should  be 
considered,  i.  e.,  plates  having  direct  contact  with  the  heated 
flue  gases  on  one  side  and  the  warm  air  current  on  the 
other.  If  these  plates  transmit  K,  B.  t.  u.  per  square  foot 
per  degree  difference  of  temperature,  tz,  per  hour;  and  if  one 
square  foot  of  grate  gives  to  the  building  E  x  f  X  P  B.  t.  u. 
per  hour,  there  will  be  the  following  ratio  between  the 
heating  surface  and  grate  surface: 

H.  8.  Efp 

(48) 
G.  K.  K  t, 

APPLICATION.— With  K  t,  —  2500  (Trans.  A.  S.  H.  &  V.  E., 
Vol.  XII,  p.  133;  also,  Jour.  A.  S.  H.  &  V.  E.,  Jan.  1916)  and  the 
same  notations  as  in  Art.  60. 

H.  S.  .6  X  14000  X  5 


=   17 


O.8.  2500 

In  practice  this  ratio  varies  anywhere  betwen  12  and  30. 

From  investigations  by  the  Federal  Furnace  League  (now 
The  National  Warm  Air  Heating-  and  Ventilating-  Association), 
furnaces  showed  an  average  o.f  \Vz  square  feet  of  direct 
heating  surface  and  1  square  foot  of  indirect  heating-  sur- 
face, making  a  total  of  2y2  square  feet  of  average  heating- 
surface  per  pound  of  coal  burned  in  the  furnaces  per  hour. 


86  HEATING  AND  VENTILATION 

In  the  tests  of  these  furnaces  combustion  rates  as  high  as 
eight  pounds  of  coal  per  square  foot  of  grate  were  obtained. 
At  this  rate  of  burning  the  ratio  of  the  heating  surface  to 
the  grate  surface  is  20  to  1.  It  is  the  opinion  of  the  author 
that  although  good  service  is  obtained  in  tests  by  combus- 
tion rates  as  high  as  eight  pounds,  furnaces  should  be 
selected  at  a  lower  value,  say  five  pounds. 

62.  Application  of  the  Above  Equations  to  a  Ten  Room 
Residence: — In  every  design,  complete  calculations  should 
be  made  and  the  results  tabulated  for  easy  reference  and 
comparison.  Such  a  tabulation  is  shown  in  Table  XII,  which 
gives  all  the  calculated  quantities  (in  some  cases  modified 
to  suit  standard  sizes)  necessary  in  the  installation  of  the 
furnace  system  illustrated  in  Figs.  17,  18  and  19.  The  value 
of  condensing  the  work  in  this  way  facilitates  checking  and 
the  detection  of  errors.  For  satisfactory  use  plans  should 
be  drawn  to  scale  and  accompanied  by  sectional  elevations. 
The  scale  should  be  large  enough  to  be  convenient  in  pro- 
ducing and  so  the  drawings  may  be  easily  read.  Locate  the 
building  with  reference  to  the  compass  points  and  state  ceil- 
ing heights  and  the  principal  dimensions  of  each  room.  The 
beginner  will  experience  some  difficulty  in  the  calculations 
in  making  proper  allowances  where  absolute  values  are  not 
obtainable,  such  as  exposures,  ceilings,  floors,  closets  and 
smaller  rooms  where  heat  is  not  provided  for.  The  personal 
element  enters  into  this  part  of  the  work  very  much  and  a 
thorough  practical  experience  is  of  great  value. 

In  estimating  O  the  simplest  and  most  convenient 
method  is  to  take  it  the  full  area  of  the  sash.  That  is  to 
say,  take  the  full  window  opening  as  glass.  Values  of  A' 
for  glass  have  been  quoted  from  .9  to  1.25  by  various  author- 
ities. It  is  the  opinion  of  the  author  that  where  the  full  win- 
dow opening  is  used  as  glass  it  will  be  best  to  make  K  —  1. 
In  Tables  VI  and  XII  this  .value  is  used.  Referring  to  the 
Living  Room,  adding  four  inches  to  the  width  and  five  inches 
to  the  height  of  each  window  gives  73  X  52  and  73  X  32 
inches  respectively  —  42  square  feet  total. 

Floor  registers  are  shown  on  the  first  floor  plans  but 
these  may  be  shifted  to  wall  registers  if  preferred.  Tabula- 
tions in  Table  XII  show  vent  registers  and  ducts  in  each 
room.  These  values  may  be  used  for  return  registers  and 
ducts  also.  Return  lines  should  be  run  from  each  second 
floor  room  excepting  Bath;  also  from  Study,  Dining  Room 


FURNACE   HEATING  87 

and  Reception  Hall  on  the  first  floor.  Increase  the  size  of 
the  return  register  in  the  Hall  from  12-in.  x  18-in.  as  calcu- 
lated to  16-in.  x  20-in.  and  omit  the  return  in  the  Living 
Room.  Vent  registers  should  be  run  to  the  attic  from  the 
Bath  Room  and  Kitchen  and  from  such  other  rooms  as  de- 
sired by  the  owner. 

Where  the  calculated  area  of  stacks  is  too  great  to  be 
included  between  the  studs  of  a  4-inch  wall,  a  6-inch  wall 
should  be  put  in.  Stacks  on  the  first  floor  are  omitted  and 
where  wall  registers  are  used,  a  floor-wall  type  is  recom- 
mended. 

The  heat  line  to  the  Bath  Room  is  a  very  bad  arrange- 
ment but  is  about  the  best  that  can  be  done  with  the  present 
room  plans.  To  overcome  the  effects  of  the  cold  wall  and 
the  resistance  of  the  offset  in  the  floor,  set  the  stack  in  an 
offset  within  the  Kitchen  and  enter  and  leave  the  floor  hori- 
zontal by  a  good  sized  turn.  Avoid  sharp  corners. 

In  selecting  the  various  stacks  and  leaders  it  may  be 
\vell  to  standardize  as  much  as  possible  and  avoid  the  extra 
expense  of  installing  so  many  sizes.  This  can  be  done  if 
the  net  area  is  not  sacrificed. 

Diameter  of  grate  allowing  ventilation  for  ten  people  = 
26  inches.  Cold  air  duct  =  600  square  inches  =  20  X  30 
inches. 


REFERENCES. — Trans.  A.  S.  H.  &  V.  E..  Rational  Methods 
Applied  to  the  Design  of  Warm  Air  Heating  Systems,  Vol. 
XXI,  p.  389.  Engineering  Data  for  Designing  Furnace  Heat- 
ing Systems,  Vol.  XXI,  p.  519. 


HEATING  AND   VENTILATION 

TABLE  XII. 
H  From  Equation  26. 


bfiS 

G 

.2 

i 

1 

I 

I 

CO 

•-  o 

T3 

1 

"ft  =5 

S  "-1 

S 

03  CM 

Ice 

S 

03  •* 

g 

"S 

> 

5" 

02 

5 

l» 

6 

6 

6 

JS 

Q 

eg 
PQ 

1 

G  .... 

42 

32 

48 

32 

16 

48 

42 

32 

32 

9 

333 

W 

263 

114 

192 

198 

390 

168 

246 

103 

148 

72 

1894 

F,  floor  or  ceiling 

195 

138 

120 

180 

194 

174 

172 

72 

1245 

H 

2 

2 

2 

2 

3 

1 

1 

1 

1 

2 

C,  cu    ft. 

1950 

2100 

1900 

1380 

1200 

1620 

1746 

1566 

936 

648 

15046 

H,  B    t    u 

15267 

9956 

12948 

12828 

14059 

10583 

11770 

9092 

8892 

5179 

110574 

N.  H.  R.,  sq.  in... 

152 

99 

129 

128 

140 

105 

117 

90 

88 

51 

H    R.,  size 

'4x16 

10x14 

12x15 

12x15 

12x18 

10x16 

12x15 

10x14 

10x14 

8x10 

II.  S.,  sq.  in. 

63 

70 

54 

53 

31 

lender,   diam  

13 

11 

12 

12 

13 

9 

10 

9 

9 

7 

AT.  R.  R. 

N.  V.R.FQ.  in.... 

106 

69 

90 

90 

140 

73 

82 

63 

62 

36 

R.  R. 

V  R  size 

10x16 

8x12 

L0xl4 

10x14 

12x18 

9x12 

1  (  )  \  1  *? 

ft  '19 

ft  -10 

R  'in 

R.  S. 

" 

" 

V.  8.  sq.  in  

84 

55 

72 

72 

78 

44 

49 

38 

38 

22 

REMARKS 

% 

3 

£ 

2  2 

ni 

E"~ 

cu 

Basement  not 

a 

3 

II 

4-> 

g 

g 

ceiled.  (First  floor, 

£> 

a 

-1 

« 

£3 

0 

£  « 

CO 

o 

floor  loss  ; 

"cu 

CP 

•*  * 

c 

a 

X 

t   0 

a 

X 

temperature  40°, 

CO 

o  > 

•O 

Hf 

J3 

f^ 

cu 

§1 

K  =  .45. 

CO 

£3 

"3  o 

cu 

cS 

•5* 

ft 

0 

id 

c 

S3  a> 

•e  § 

-o 

Attic  floored 

0 

OX3 

3 

^  >» 

2s 

t_ 

cS 

5*" 

03 

solid.    (Second 

•3 

1 

o-g 

«  — 

'   O 

I 

1 

-s" 

CO 

floor,  ceiling  loss  ; 

1 

«  i 

07 

S  ft 

™  a 

CU 

3 

"y 

i" 

o 

13 

temperature  20°, 

0 

0.3 

Q 

£  t" 

S  3 

G 
^ 

O  — 

8* 

So 

K  =  .25 

£ 

cu 

^=2 

-  S 

0 

x* 

O 

•»^ 

o 

G 

• 

CO 

+i   ^ 

8>, 

cu  C 

^  »c 

<B 

0  0 

fi 

cu  "S 

-  .2  .S 

y_0 

G 

M** 

G 

h* 

*"  <w 

S 

o 

•a"^'" 

co  C 

03  "S 

CO 

"s  ec 

0 

c  •*•* 

"etf  « 

S?  s 

|S 

f£  cu 

^ 

—  3 

^ 

a 

X 

•5  e 

a 

i  ^ 

=s|^ 

tt)    CJ 

=  2 

cu 

"5  *5 

a 

CD 

a 

1! 

o 

o 

H 

CIO 
OrH 

III 

ii 

+j  £ 

rf;  E-. 

c 

T3 

If 

10 

o 

0 

^ 

•o-o 

^ 

X 

^O  **-" 

•d  • 

•O 

DO 

2; 

•*s! 

<!<! 

=2 

y 

< 

< 

FURNACE   HEATING 


89 


FOUNDATION   PLAN 

CEILING    7  ' 

Figr.  17. 


00 


HEATING  AND  VENTILATION 


t  FIRST.  FLOOR  PLAN 
E         CEILING     IO' 


Fig-.  18. 


FURNACE   HEATING 


1)1 


SECOND  FLOOR  PLAN 


CEILING     9' 

L 


92  HEATING  AND   VENTILATION 

63.  Determination  of  the  Best  Outside  Temperature  to 
Use  in  Design  and  the  Costs  Involved  in  Heating  by  Fur- 
naces:— As  a  basis  for  the  work  of  the  heating  and  ven- 
tilating engineer  it  is  necessary  that  he  be  well  acquainted 
with  the  temperature  conditions  in  the  locality  where  his 
services  are  employed.  He  should  compile  a  chart  showing 
extreme  and  average  temperatures  covering  a  period  of 
years  and  with  this  chart  a  fairly  safe  estimate  may  be 
made  upon  the  costs  involved  in  operating  any  heating  and 
ventilating  system  during  any  part  of  the  average  season 
or  throughout  the  entire  heating  season.  Any  estimated 
costs  of  operation  are  only  illustrative  of  method  and  prob- 
ability. All  one  can  say  is  that  if  the  temperature  in 'any 
one  season  averages  what  is  shown  by  the  average  curve  for 
the  period  of  years  investigated,  the  cost  in  operating  the 
system  may  be  easily  shown  by  calculation.  Heating  costs 
are  relative  values  only  and  cannot  be  determined  exactly 
except  under  test  conditions. 

The  heating  engineer  should  also  know  the  minimum 
outside  temperatures  covering  a  period  of  years  in  that 
locality  to  determine  an  outside  temperature  for  his  design 
•work.  Every  design  is  a  compromise  between  average  and 
extreme  conditions,  approaching  the  extreme  rather  than  the 
average.  Patrons  expect  heating  systems  to  be  designed  to 
give  normal  temperatures  in  the  rooms  on  all  but  a  few  of 
the  coldest  days.  Extremely  low  temperature  conditions 
have  a  duration  of  from  two  to  three  days  and  it  would  not 
be  good  engineering  from  an  economic  standpoint  to  design 
the  system  large  enough  to  heat  to  normal  inside  tempera- 
ture on  the  coldest  day  experienced  in  a  period-  of  years. 
The  plant  would  be  too  large  and  would  require  too  much 
financial  input.  As  an  illustration  of  the  method  of  obtain- 
ing the  outside  temperature  to  be  used  in  design,  also  meth- 
ods of  determining  approximate  costs  for  heating,  see  Fig. 
20.  The  low  central  curve  is  plotted  from  the  average  tem- 
peratures on  each  of  the  days  respectively  between  Septem- 
ber fifteenth  and  May  fifteenth,  covering  a  period  of  thirty 
years,  at  Lincoln,  Nebraska.  The  minimum  temperature  for 
December,  1911,  and  January,  1912,  (regarded  as  a  period  of 
unusual  severity)  are  included.  Referring  to  the  chart  it 
will  be  seen  that  this  cold  period  reached  its  minimum  tem- 
perature of  — 26°  on  January  twelfth.  Assuming  this  curve 
to  represent  the  most  severe  weather  in  this  locality,  a  study 


FURNACE   HEATING  93 

of  conditions  may  easily  determine  the  best  outside  tempera- 
ture to  be  used  in  design.  There  were  twenty  days  when 
the  temperature  was  below  zero,  twelve  days  below  — 5°, 
six  days  below  — 10°,  two  days  below  — 20°,  and  part  of  one 
day  below  - — 25°.  Each  of  the  extreme  and  sudden  drops 
were  such  as  to  last  from  two  to  three  days  and  were  only 
experienced  in  two  or  three  instances.  It  is  very  evident 
that  a  system  designed  for  0°  outside  would  fall  short  of 
the  requirement  even  when  put  under  heavy  stress.  On  the 
other  hand  one  designed  for  — 25°  outside  would  actually 

TEMPERATURE-CHART-AND-HEAT-LOSS-FOR-AVERACE-YEAR. 

SEPT      OCT  NOV  DEC  JAN  FE8  MAR  APR 


Fig.  20. 

come  up  to  its  capacity  for  only  a  part  of  one  day  out  of 
the  240  heating  days.  One  designed  for  — 10°  would  fulfill 
conditions  without  forcing  excepting  at  two  or  three  periods 
of  very  short  duration,  at  which  times  the  system  could  be 
forced  sufficiently  without  detriment.  The  personal  equa- 
tion enters  into  the  calculation  of  the  heat  loss  somewhat 
and  there  will  be  some  difference  of  opinion  concerning 
which  to  use,  — 10°  or  — 15°.  Probably  the  latter  would  be 
a  safer  value.  All  that  is  necessary  is  to  plan  for  ample 


!)4  HEATING  AND  VENTILATION 

service  at  all  but  one  or  two  of  the  cold  periods  of  short 
duration  and  the  system  will  be  considered  very  satisfactory 
from  the  standpoint  of  size  and  capacity.  Any  additional 
amount  put  in  would  be  an  investment  of  money  which  is 
scarcely  justified  for  the  small  percentage  of  time  that  this 
additional  capacity  would  be  called  for. 

After  the  minimum  outside  temperature  has  been  de- 
cided and  the  plant  is  designed  one  would  like  to  know  the 
probable  expense  in  handling1  such  a  plant  throughout  the 
heating  season.  Assume  an  inside  temperature  throughout 
the  building  of  70°.  Combine  the  two  half  months.  September 
and  May,  into  one  month,  and  take  the  average  of  these 
average  temperatures  for  the  days  of  each  month,  thus  giv- 
ing the  drop  in  temperature  between  the  inside  and  the  out- 
side of  the  building.  The  heat  loss  from  the  building  is 
approximately  proportional  to  these  drops  in  temperature. 
In  this  case  the  differences  are  as  follows: 

September  +  May  7°       below  70° 

October   17°       below  70° 

November  32.3°   below  70° 

December   44°       below  70° 

January  48.7°   below  70° 

February    45°      below  70° 

March    34°       below  70° 

April    19.5°   below  70° 

Taking  the  sum  of  all  these  differences  as  the  total,  100  per 
cent.,  and  dividing  each  individual  difference  by  the  total, 
we  have  the  percentages  of  loss  for  the  various  months  as 
follows: 

September   +    May 2.84  per  cent,  of  total  yearly  loss 

October    6.86        "  "       "  "         " 

November  13.05        "  "       "  "         " 

December    17.77       "  "       "  "         " 

January  19.67        "  "       "  "         " 

February  18.20 

March    18.71 

April  7.90 

Total 100.00 

These  percentages  of  loss  indicate  what  may  be  expected 
in  the  expense  for  coal  for  the  respective  months  of  the 
average  heating  year  in  the  locality  stated.  Upon  this 


FURNACE   HEATING 


05 


basis,  Fig.  20  represents  an  application  of  the  above  to  a 
residence  having  a  heat  loss,  H,  approximating  100000  B.  t.  u. 
per  hour.  The  results  are  shown  in  B.  t.  u.  loss  and  in  tons 
of  coal  per  year,  assuming  that  the  entire  house  is  heated  to 
70°  upon  the  inside  for  each  hour  between  September  fif- 
teenth and  May  fifteenth.  The  lowest  curve  is  that  for 
direct  radiation  only.  The  next  superimposed  curve  assumes 
outside  air  for  ten  people.  The  third  curve  assumes  one-half 
of  the  required  air  to  be  recirculated  and  the  upper  curve 
assumes  all  the  air  to  be  from  the  outside. 

64.  Filtering,  Washing  and  Humidifying  Furnace  Air: — 
Two  objections  frequently  urged  against  indirect  heating 
are  the  dust  content  and  the  dryness  of  the  circulated  air. 
It  is  possible  to  overcome  both  of  these  objections  in  the 
larger  mechanical  plants,  but  in  small  furnace  plants  where 
the  circulated  air  moves  wholly  by  convection  but  little 
progress  has  been  made.  Cheesecloth  screens,  fibrous  ma- 
terial such  as  unbraided  ropes,  linen  strips  and  soft  wicking, 
kept  moist  by  water  drips,  may  be  used  for  filtering.  To 
offset  the  air  resistance  due  to  the  filter,  the  cross  sectional 
area  of  the  duct  at  the  filter  should  be  at  least  four  times 
the  net  area  of  the  duct,  for  cheesecloth  and  fibrous  mate- 
rial, and  twice  the  net  area  for  linen  strips  and  wicking. 
The  filter  should  be  frequently  cleaned  by  flushing.  Where 
water  pressure  from  city  supply  or  pump  is  available,  sprays 
,-,  are  more  satisfactory  than  the  filter.  The  essentials 

of    a    small    residence    air    washing    plant    are: 
pressure    water    supply,    electric    current,    wash- 
ing chamber  and  drain- 
Fig.    21,    a    shows 


age. 


City  Water 
Supply 


HEATING  AND  VENTILATION 


a  simple  arrangement.  Having  given  a  furnace  heating 
plant,  provide  an  air  mixing  chamber  for  the  fresh  and  recir- 
culated  air,  install  a  spray  head  (a  1/4-  or  %-inch  pipe  built 
in  the  form  of  an  ell  or  tee,  with  the  ends  plugged  and  the 
bottom  drilled  with  sV-inch  holes),  from  this  spray  head  sus- 
pend unbraided  ropes,  hemp  strands,  linen  strips,  wicking 
or  layers  of  cheesecloth  kept  wet  by  water  drips  and  com- 
pel the  air  to  weave  its  way  through  these  wetted  surfaces 
to  the  furnace.  Much  of  the  dust  and  other  mechanically 
suspended  particles  in  the  air  will  be  deposited  on  the 
fibrous  material  and  finally  washed  to  the  sewer.  Because 
of  the  low  pressure  head  moving  the  air  in  such  a  plant  no 
unnecessary  resistances  should  be  put  in.  The  chief  objection  to 
the  system  shown  is  the  water  waste  which  may  be  any 
amount,  from  just  enough  drips  to  keep  the  eliminators 
moist,  to  the  full  jet- outlet  under  pressure.  Water  waste 
may  be  almost  wholly  eliminated  by  catching  it  in  a  metal 
basin  and  recirculating  it  by  means  of  a  small  electric  pump, 
as  in  Fig.  21,  &.  But  here  again  is  the  expense  of  operating 
the  electric  motor  arid  the  cost  of  the  small  amount  of  water 
that  is  thrown  away  when  flushing  and  refilling.  The  oper- 
ating expense  in  any  of  these  systems  is  not  excessive  as 
shown  under  the  application.  Where  air  washing  is  not  con- 
sidered, humidity  conditions  may  be  cared  for  by  evaporating 

pans  as  suggested  by 
Figs.   22,    (n)   and    (&). 


Fig.  22. 


(b) 


APPLICATION. — A  ten-room  residence  circulating  not  to  ex- 
ceed 100000  cubic  feet  of  air  per  hour  has  a  fresh  air  duct 
(or  recirculating  duct)  4.2  square  feet  in  cross-sectional 
area.  Because  of  the  resistance  offered  to  the  circulating 
air  let  the  area  be  16  square  feet  at  the  filter,  say  4-ft.  x  4-ft. 
Let  the  spray  head  be  a  single  line  4  feet  long  with  ten, 
e^ -inch  holes  on  the  under  side.  What  will  it  cost  to  operate 
such  a  washing  plant  for  a  day  of  15  hours  under  maximum 


FURNACE   HEATING  97 

water  flow  by  each  of  the  two  systems,  i.  e.,  the  waste  water 
system,  where  the  water  is  run  to  the  sewer  continuously, 
and  the  recirculating  system  where  the  only  loss  is  that  due 
to  occasional  flushing.  City  water  may  be  assumed  to  have 
a  pressure  of  50  pounds  per  square  inch  and  to  cost  15  cents 
per  1000  gallons.  Electric  current  may  be  had  for  10  cents 
per  K.  W.  At  a  gage  pressure  of  50  pounds,  a  ^r-inch  hole 
will  jet  approximately  one  cubic  foot  of  water  (62.5  Ibs.)  per 
hour.  Ten  holes,  therefore,  will  "waste  to  the  sewer  625 

75 

pounds  (75  gals.)  per  hour.     This  water  will  cost  15  X  = 

1000 
1.125  cents  per  hour,  or  16.8  cents  for  a  15-hour  day. 

The  electric  motor  pump  may  be  made  to  circulate  a 
sufficient  amount  of  "water  without  waste,  at  a  pressure 
much  less  than  50  pounds.  For  comparative  values  in  cal- 
culation call  the  pressures  the  same.  With  an  efficiency  of 
the  motor  pump  40  per  cent.,  the  work  done  per  hour  by  the 
motor  is  (625  X  50  X  2.3  X  .746)  -f-  (33000  X  60  X  .40)  = 
.068  K.  W.  At  ten  cents  per  K.  W.  this  is  .68  cent  per  hour 
or  10.2  cents  for  a  15-hour  day.  No  allowance  is  here  made 
for  the  small  amount  of  friction  loss  in  the  nozzles  and 
pipes  as  these  vary  greatly  with  the  amount  of  pipe  and  the 
pressure  under  which  the  system  is  run.  The  amount  lost 
in  evaporation  is  the  same  in  each  case. 

In  the  two  estimated  values,  that  for  the  waste  water 
system  would  probably  decrease  in  the  average  plant  be- 
cause of  a  saving  of  water  by  throttling  the  supply,  while 
that  for  the  pumping  plant  would  probably  increase  slightly. 
A  very  fair  estimate  in  either  case  is  one  cent  per  hour  for 
maximum  service.  This  is  sufficiently  large  to  allow  for  a 
material  increase  in  the  number  of  the  jets  above  that  given. 

Where  an  electric  motor  pump  is  used  to  circulate  the 
water  or  where  the  city  supply  is  used  without  throttling, 
the  filters  may  be  omitted,  the  duct  may  be  uniform  in  sec- 
tion and  the  spray  head  may  be  located  across  the  bottom  of 
the  opening  with  the  holes  pointing  toward  the  top  of  the 
duct.  In  this  way  the  spray  is  broken  up  by  contact  with 
the  deflector  at  the  top  of  the  duct  and  falls  as  a  mist, 
through  the  air  current. 

It  would  be  of  interest  here  to  briefly  discuss  the  prob- 
able temperature  and  humidity  effects  upon  the  circulating  air 
within  the  residence  if  a  washing  plant  of  this  character 
were  installed.  This  section  is  offered  as  a  fair  probability 


98  HEATING  AND   VENTILATION 

in  the  absence  of  collected  data.  For  basis  of  argument, 
assume  the  following:  100000  cubic  feet  or  air  circulated 
per  hour  at  the  register,  register  temperature  120°,  no  re- 
circulated  air  used,  temperature  outside  50°,  temperature 
inside  70°,  humidity  outside  50  per  cent.,  humidity  inside  45 
per  cent.  What  amount  of  water  is  absorbed  per  hour? 

100000  cubic  feet  of  air  at  120°  at  the  register  is  equiv- 
alent to  87930  cubic  feet  at  50°  on  the  outside  and  91380 
cubic  feet  at  70°  in  the  room.  The  amount  of  moisture  in  a 
cubic  foot  of  saturated  air  on  the  outside  at  50°  is  4  grains 
and  at  50  per  cent,  saturation  would  be  .50  X  4  =  2  grains. 
Correspondingly  in  the  room  air  at  saturation  we  have  7.98 
grains  and  at  45  per  cent,  humidity  .45  X  7.98  =  3.59  grains. 
The  total  amount  of  moisture  in  the  incoming-  air  is  87930  X 
2  =  175860  grains  (25.12  Ibs.)  per  hour.  The  total  amount 
of  moisture  in  the  room  air  is  91380  X  3.59  =  328054  grains 
(46.8  Ibs.)  per  hour.  It  is  evident  that  the  difference  be- 
tween these  two  amounts  (46.8  —  25.12  =  21.73  Ibs.)  has 
been  added  per  hour  from  the  washing  water  (See  Art.  27). 
In  this  way  the  weight  of  water  absorbed  may  be  worked 
out  theoretically  for  any  temperatures  and  for  any  humidities. 
The  actual  amounts  absorbed,  however,  may  vary  consider- 
ably from  the  theoretical  figures  because  of  the  wide  range 
in  temperatures  and  humidities  between  the  incoming  and 
outgoing  air  and  the  shortness  of  time  the  air  is  in  actual 
contact  with  the  water. 

Close  regulation  of  the  humidity  of  such  a  plant  is  a  diffi- 
cult problem.  The  humidostat,  if  used,  necessarily  acts  to 
control  the  amount  of  water  flowing.  When  the  humidity 
is  high  this  cuts  off  the  flow  of  water,  in  which  case  the 
apparatus  ceases  to  serve  as  a  washer.  From  what  is 
known  of  such  plants  it  is  probable  that  the  humidity  of 
the  air  after  passing  the  furnace  is  never  high  enough  to 
give  much  concern  and  the  humidostat  may  be  eliminated. 
The  location  of  the  spray  head,  in  the  cool  air  chamber,  re- 
tards the  absorption  process  because  cool  air  takes  up 
moisture  with  less  freedom  than  warm  air.  Even  assuming 
that  the  cool  air  is  fully  saturated  as  it  enters  the  furnace, 
the  humidity  will  drop  so  rapidly  as  the  air  is  heated  that 
there  will  never  be  any  danger  of  depositing  moisture  on 
the  furniture  of  the  room.  To  illustrate.— In  the  above 
problem  assume  that  the  50°  air  is  saturated  as  it  enters 
the  furnace  (a  condition  it  will  seldom  reach).  When  heated 


FURNACE   HEATING  99 

to  70°  the  humidity  will  be  52  per  cent.,  which  is  a  very  sat- 
isfactory amount.  Again,  if  the  outeide  air  is  60°  and  sat- 
urated as  it  enters  the  furnace,  the  humidity,  when  raised 
to  70°  will  be  75  per  cent.,  an  amount  that  would  still  cause 
the  air  to  be  agreeable.  Now  what  happens  at  low  tempera- 
tures? If  the  entering  air  is  saturated  at  40°,  the  humidity 
at  70°  would  be  37  per  cent.  From  this  it  would  seem 
that  a  humidostat,  for  the  purpose  of  controlling  the  moist- 
ure, would  be  of  very  little  service  unless  the  air  were  cir- 
culated for  purposes  of  ventilation  at  or  near  70°  and  satura- 
tion, a  state  of  affairs  very  seldom  asked  for  in  residence 
work. 


CHAPTER   V. 


FURNACE    HEATING   AND    VENTILATING. 


SUGGESTIONS  ON   THE    SELECTION  AND   INSTALLATION 
OF    FURNACE    HEATING    PARTS. 

65.  The  Furnace: — Furnaces  for  residences  are  usually 
of  the  portable  type,  illustrated  by  Fig.  23.  This  consists  of 
a  heating"  stove  enclosed  in  a  shell  composed  of  two  metal 
casings  having  a  dead  air  space  or  an  asbestos  insulation  be- 
tween them.  Some  of  the  larger  furnaces  used  in  the  larger 
residences,  small  -schools,  etc.,,  have  permanent  casements 
of  brick  work  as  in  Fig.  24.  Both  types  of  furnaces  give 


Fig.  23. 

good  results.  The  points  usually  governing  the  selection  be- 
tween portable  and  permanent  settings  are  required  capac- 
ity, price  and  available  floor  space. 

The  stoves  are  made  of  cast  iron,  wrought  iron  and 
steel.  The  cast  stove  admits  of  a  greater  variety  of  shapes 
than  those  made  of  rolled  plates  hence  it  is  more  commonly 


FURNACE    HEATING 


101 


used.  The  sections  are  asseinoled  vrita.  ccrretiit,eJ  joiats 
while  the  rolled  sections  are  riveted.  The  chief  objection 
to  the  cast  stove  is  the  frequent  leakage  of  fuel  gases  from 
the  combustion  chamber  to  the  warm  air  passages.  In  a 
properly  designed  and  set  up  cast  furnace  there  should  be 
little  excuse  for  leakage.  When  it  does  occur,  examine  the 
cement  in  all  the  joints  especially  around  the  door  openings. 
It  is  claimed  by  some  that  the  heated  cast  iron  plates  permit 
the  passage  of  some  of  the  gases  directly  through  the  metal. 
While  this  may  be  true  to  a  certain  degree  in  comparison 
with  rolled  materials  such  as  steel,  there  is  little  doubt  that 
practically  all  leakage  can  be  traced  to  cracked  sections  or 
to  broken  cement  joints.  In  general,  the  fewer  the  joints 


Fig.  24. 

in  a  furnace  stove  the  better.  On  the  other  hand  cast  iron 
corrodes  less  than  rolled  plate  and  the  heavy  cast  walls  of 
this  type  act  as  a  storage  for  heat  and  tend  toward  less 
fluctuation  of  air  temperature. 

Furnaces  are  direct-draft  and  indirect-draft.  In  the  direct- 
draft  type  the  radiator  (heat  distributor)  is  above  the  firo 
and  the  gas  passages  are  usually  short  and  fairly  direct  to 
the  chimney.  In  the  indirect-draft  type  the  radiator  is  be- 
low the  fire  and  the  gases  are  first  deflected  downward  over 
the  radiator  and  then  upward  to  the  chimney.  In  this  type 
there  should  always  be  a  by-pass,  properly  dampered,  so 
that  when  there  is  a  lack  of  draft  due  to  a  cold  chimney 


102  HEATING   AN-D^VENTILATK  )X 

(unual.i^'^'fpti^Vl.JwhJ&ti.sCarf-tiVi^'a  new  fire)  or  other  cause  the 
gases  may  be  given  a  short  cut  to  the  chimney  removing 
excess  friction  and  avoiding  smoking.  An  indirect-draft 
furnace  should  be  used  only  on  a  protected  or  enclosed  chim- 
ney. In  cases  where  sufficient  draft  Is  sure  at  all  times  this 
type  of  furnace  is  probably  the  most  economical. 

The  cylindrical  fire  pot  is  better  than  a  conical  or  spher- 
ical one,  there  being  less  danger  of  the  fire  clogging  and 
becoming  dirty.  A  lined  fire  pot  is  better  than  an  unlined 
one,  because  a  hotter  fire  may  be  maintained  in  it  \vith  less 
detriment  to  the  furnace  and  less  contamination  of  the  air 
supply.  There  is  a  loss  of  heating  surface  in  the  lined  pot, 
however,  and  in  most  furnaces  the  fire  pot  is  unlined  to  ob- 
tain this  increased  heating  surface. 


Fig.  25. 

Some  form  of  shaking  or  dumping  grate  should  be  se- 
lected, as  a  stationary  grate  is  far  from  satisfactory.  Care 
should  be  exercised  in  the  selection  of  the  movable  grate, 
as  some  forms  not  only  stir  up  the  fire  but  permit  much  of 
it  to  fall  through  to  waste  when  being  operated. 

In  most  furnaces  the  fuel  is  fed  to  the  fire  pot  from  a 
door  above  the  fire.  These  are  called  top-feed  furnaces.  In 
some  fo»rm.s  the  fuel  is  fed  up  through  the  center  of  a  rotary 
ring  grate.  These  are  called  under-feed  furnaces  (Fig.  25) 
and  for  the  finer  grades  of  coal  are  preferred  to  the  top-feed 
furnaces. 

The  size  of  the  furnace  for  any  given  work  may  be  ob- 
tained from  the  estimated  heating  capacity  in  cubic  feet  of 


FURNACE   HEATING 


103 


room  space  as  given  in  Table  20,  Appendix.  A  better  and 
safer  way,  and  one  that  serves  as  a  good  check  on  the 
above,  is  to  select  the  furnace  from  the  calculated  grate  area 
(See  Art.  60). 

A  comlrliu'.ticn  furnace  and  heater  is  shown  in  Fig1.  26.  With 
it  some  of  the  rooms  of  a  residence  may  be  heated  by  warm 
air  and  the  remainder  by  hot  water  or  steam.  In  this  way 
rooms  to  be  ventilated  as  well  as  heated  may  be  connected 
by  the  proper  stacks  and  leaders  to  the  warm  air  deliveries, 
while  rooms  requiring  less  ventilation  or  heat  only,  or  those 
rooms  that  are  difficult  to  heat  with  air  circulation  may 
have  radiators  installed  and  connected  to  the  flow  and  re- 
turn pipes  of  the  water  or  steam  system. 


Fig.  26. 

Pipeless  furnaces  are  manufactured  and  installed  in  stores, 
small  residences  and  the  like.  In  this  type  the  stove  is  sur- 
rounded by  two  independent  casings  instead  of  one  as  in  the 
pipe  furnace,  heated  air  circulating  upward  between  the 
stove  and  the  inner  casing  and  return  air  downward  between 
the  casings.  The  top  of  the  furnace  terminates  in  a  short 
stack  capped  by  a  combination  hot-and-cold  air  register  at 
the  floor  line  of  the  first  floor  room.  The  central  zone  of 
the  register  supplies  air  to  the  room  and  the  outer  ring  zone 


104 


HEATING  AND  VENTILATION 


carries  cold  air  from  the  room  to  the  furnace.  All  air  is  de- 
livered to  one  room  and  from  here  circulates  to  and  from 
the  other  rooms  of  the  house  through  transoms,  open  doors, 
etc.  Fig".  27  shows  the  principle  of  operation.  Compared 
with  other  furnace  plants  the  application  of  this  type  is 


Fig".  27. 

much  simpler  and  the  installation  cost  is  less.  Its  satis- 
factory application  is  limited  to  those  buildings  having  open 
interior  construction  where  the  furnace  may  be  centrally 
located  and  where  every  room  has  continuous  opening  to  the 
room  above  the  furnace.  Furnaces  of  this  type  are  good 
heaters  but  have  no  ventilating  possibilities.  One  of  the 
objections  usually  found  with  this  type  of  furnace  is  the 
presence  of  floor  drafts  in  the  room  above  the  furnace.  Since 
bath  rooms,  toilet  rooms,  laundries  and  kitchens  are  usually 
not  connected  to  the  return  circulation,  these  rooms  are  dif- 
ficult to  heat  from  the  pipeless  furnace. 

Room  Heaters  (slightly  modified  forms  of  standard  fur- 
naces) may  be  obtained  for  use  in  small  buildings  having  no 
basements.  Such  furnaces  should  have  well  insulated  metal 
jackets  to  protect  the  nearby  room  furnishings  from  exces- 
sive heat.  The  circulating  air  may  be  taken  from  the  out- 


FURNACE   HEATING  105 

side  of  the  building  in  about  the  same  way  as  a  direct-in- 
direct radiator  (See  Art.  102),  or  may  be  recirculated  from 
the  room,  entering-  the  bottom  of  the  furnace  at  the  floor 
line  through  a  register  base,  and  leaving  from  the  wide 
open  top  of  the  furnace.  A  vent  flue  for  the  room  is  usually 
provided  by  the  side  of  or  in  connection  with  the  chimney  or 
smoke  flue.  Room  heaters  are  naturally  not  desired  be- 
cause of  their  appearance  but  they  are  effective  heaters  and 
where  properly  installed  may  give  fair  ventilating  effect. 
The  one  serious  objection  to  the  room  heater,  other  than  its 
appearance,  is  the  presence  of  floor  drafts  as  in  the  pipeless 
furnace. 

One  of  the  most  important  points  in  the  selection  of  any 
furnace  is  its  cleaning  possibilities.  If  there  is  a  probability 
that  soft  coal  may  be  used  at  any  time  the  furnace  should 
be  provided  with  clean-outs  so  situated  that  all  parts  of  the 
gas  passages  may  be  reached  by  flue  swabs. 

Care  must  be  exercised  also  in  the  installation  of  the 
furnace  to  protect  the  nearby  combustible  material  from 
fire.  Smoke  pipes,  especially,  must  have  ventilated  thimbles 
giving  at  least  2-inch  air  space  all  around  the  pipe  where 
passing  through  combustible  walls. 

66.  Location  and  Setting  of  the  Furnace: — A  furnace 
should  be  set  as  near  the  center  of  the  house  plan  as  pos- 
sible. Where  this  can  not  be  done,  preference  should  be 
given  to  the  colder  sides  (sides  subjected  to  the  heaviest 
winter  winds),  in  most  localities  the  north  and  west.  In 
any  case,  it  is  advisable  to  have  the  leader  pipes  of  uniform 
length  and  pitch  if  possible.  The  smoke  pipe  should  be 
short,  but  it  is  better  to  have  a  moderately  long  smoke  pipe 
and  obtain  a  more  uniform  length  of  leaders  than  to  have  a 
short  smoke  pipe  and  leaders  of  widely  different  lengths. 

The  furnace  should  be  set  low  enough  to  give  a  good 
upward  slope  to  the  leaders  from  the  furnace  to  the  respec- 
tive stacks.  This  should  be  not  less  than  one  inch  per  foot  of 
length  and  more  if  possible.  Each  leader  should  be  dampered 
near  the  furnace. 

The  location  of  the  furnace  will  call  forth  the  best 
judgment  of  the  designer,  since  a  right  or  wrong  decision 
here  is  very  vital. 

FOUNDATION. — All  furnaces  should  have  the  manufactur- 
er's directions  to  govern  the  setting.  Such  information  is 


106 


HEATING  AND  VENTILATION 


usually  followed.  In  every  case  the  furnace  should  be 
mounted  on  a  level,  brick  or  concrete  foundation  especially 
prepared  and  well  finished  with  cement  mortar  on  the  inside, 
since  this  interior  is  in  contact  with  the  fresh  air  supply. 

67.  Fresh  Air  Duct: — Ducts  below  the  floor  are  best 
constructed  of  hard  burned  brick  walls  4  inches  thick,  con- 
crete walls  2  to  3  inches  thick  or  vitrified  tile;  the  floors  to 
be  not  less  than  1-inch  concrete  and  the  tops  to  be  1-  to  2- 
inch  concrete  slabs.  The  walls  and  floors  of  the  brick  or 
concrete  ducts  should  be  smooth  plastered  with  neat  cement 
and  all  joints  should  be  tight. 

Ducts  above  the  floor  are  usually  made  of  galvanized 
iron.  Where  made  of  boards  they  should  be  solid  material 
well  tongued  and  grooved.  The  riser  from  the  main  hori- 
zontal to  the  outside  of  the  building  may  be  of  wood,  tile 
or  galvanized  iron  and  the  fresh  air  inlet  should  be  ver- 
tically screened.  The  whole  fresh  air  line  should  have  tight 
joints  and  should  be  so  constructed  as  to  be  free  from  sur- 
face drainage,  dirt,  rats  and  other  vermin. 


FRONT 


FRONT 


FRONT 

Fig.  28. 

In  addition  to  the  opening  for  the  admission  of  the 
fresh  air  duct,  another  opening  or  openings  may  be  made 
under  the  furnace  for  the  purpose  of  admitting  the  duct 
which  carries  the  recirculated  air  from  the  rooms  to  the 
furnace  (See  Fig.  28).  Occasionally  the  two  ducts  unite  in 
a  Y  fitting  before  entering  the  furnace,  in  which  case  the 
fitting  should  be  so  constructed  as  to  make  the  two  uniting 
streams  of  air  enter  as  nearly  parallel  as  possible.  Each  of 
these  ducts  should  have  adjustable  dampers  so  as  to  make 
them  independent  of  the  other.  Each  duct  also  should  be 
provided  with  a  door  that  can  be  opened  temporarily  to  the 
basement  for  inspection  and  cleaning.  Sometimes  it  is  de- 


FURNACE   HEATING 


107 


sirable  to  have  two  or  more  fresh  air  ducts  leading  from 
the  different  sides  of  the  house  to  get  the  benefit  of  any 
change  in  air  pressure  on  the  outside  of  the  building  (See 
also  Figs.  16  and  17). 

Arrangements  may  be  made  for  pans  of  clear  water  in 
the  air  duct  entering  the  furnace  (See  Art.  64)  to  give 
moisture  to  the  air  current,  but  it  should  be  understood  that 
only  a,  small  amount  of  moisture  will  be  taken  up  at  this 
point  from  still  water  surfaces.  In  most  cases  where  mois- 
tening pans  (commonly  called  water  pans)  are  used,  they  are 
installed  in  connection  with  the  furnace  itself.  Furnaces 
should  have  special  means  provided  for  moistening  the  cir- 
culated air.  The  water  pan  is  a  step  in  the  right  direction, 
but  this  alone  is  not  sufficient  (See  Art.  27). 

68.  Recirculatiiig  Ducts: — Ducts  should  be  provided 
from  the  rooms  within  the  building,  through  the  basement 
to  the  bottom  of  the  furnace.  These  ducts  carry  the  air  from 
the  rooms  back  to  the  furnace  to  be  reheated  for  use  again 
within  the  building.  Recirculating  the  air  gives  a  more  positive 
type  of  heating  system.  Rooms  difficult  to  heat  without  recir- 
culatipn  are  improved  with  its  use  and  rooms  at  a  distance 
from  the  furnace  should  always  have  it.  Frequently  a  num- 
ber of  rooms  are  grouped  together  on  one  return  line.  Small 
residences  may  have  but  one  return  line  leading  from  the 
return  register  in  the  front  hall  near  the  door.  Return  lines 
should  be  grouped  in  -the  base- 
ment to  simplify  the  system  and 
to  avoid  making  many  openings 
into  the  furnace  foundation.  Re- 
turn stacks  should  be  light  tin  or 
galvanized  iron  built-in  between 
the  studding  of  the  outside  walls 
and  need  not  be  insulated.  Con- 
tractors usually  omit  these  metal 
ducts  between  the  studs,  and  the 
dust  from  the  rooms  settling  on 
the  rough  surfaces  of  the  studs 
and  sheathing  makes  an  unsani- 
tary condition.  In  like  manner 
horizontals  in  the  basement  are 
frequently  slighted  by  tinning  un- 
der two  adjoining  joists  thus 
Fig.  29.  forming  the  duct.  Such  construe- 


108 


HEATING  AND   VENTILATION 


tion  should  not  be  permitted.  All  vertical  return  lines  and  all  ex- 
posed horizontal  runs  between  the  return  registers  in  the  rooms  and 
the  attachment  at  the  furnace,  should  be  tin  or  galvanized  iron  with 
tight  joints.  (See  Fig-.  29).  Avoid  overhead  return  ducts  near 
the  furnace.  In  some  installations  it  is  necessary  to  carry 
these  ducts  along  the  basement  ceiling  part  way  across  the 
basement  but  the  drop  to  the  floor  should  be  made  at  such  a 
distance  from  the  furnace  that  the  air  in  the  vertical  return 
will  not  be  retarded  in  its  fall  by  the  heat  from  the  furnace. 
69.  Leaders: — All  leaders  should  be  round  and  free 
from  unnecessary  turns.  They  should  be  made  from  No.  24 
or  No.  26  galvanized  iron  or  tin,  should  be  run  as  straight 
as  possible  and  should  be  well  supported.  Connections  with 


Fig.  30. 

the  furnace  should   be   straight,  but   if  a   turn   is  necessary, 
provide    long    radius    elbows.      All    connections    to    risers    or 


FURNACE   HEATING 


109 


stacks  should  be  made  through  long"  radius  elbows.  Rec- 
tangular shaped  boots  having  attached  collars  are  frequently 
used  but  these  are  not  satisfactory  because  of  the  impinge- 
ment of  the  air  against  the  flat  side  of  the  stack;  also,  be- 
cause of  the  danger  of  the  leader  entering  too  far  into  the 
stack  and  shutting  off  the  draft.  Leaders  should  connect  to 
first  floor  registers  by  long  radius  elbows.  Leaders  should 
have  as  few  joints  as  possible  and  these  should  be  made  firm 
and  air  tight.  Fig.  30  shows  different  methods  of  connecting 
between  leaders  and  stacks,  and  between  leaders  and  regis- 
ters. 

Leader  pipes  should  be  covered  to  avoid  heat  loss  and  to 
provide  additional  safety  to  the  plant.  The  covering  usually 
put  on  is  one  or  two  thicknesses  of  asbestos  paper  laid  with 
face  contact.  As  a  heat  insulator  this  is  little  better  than 
the  bare  pipe.  A  better  way  is  to  have  the  layers  of  as- 
bestos paper  separated  by  spiral  wrappings  of  wire,  air  cell 
material  or  mineral  wool  to  give- dead  air  spaces.  Leaders 
passing  through  combustible  walls  must  have  ventilated 
thimbles,  giving  at  least  a  1-inch  air  space  all  around  the 
leader. 

70.     Register  Connections: — The  most  efficient  first  floor 


Fig.  31. 

warm  air  intake  is  through  a  floor  register.  Fig.  31  a  shows 
a  galvanized  floor  box  enclosing  a  floor  register  and  con- 
nected to  the  leader  by  a  round  elbow.  Floor  registers  give 


110 


HEATING  AND   VENTILATION 


the  freest  circulation  that  can  be  obtained  in  first  floor  fur- 
nace heating-,  but  they  are  dust  catchers  and  unsanitary; 
also,  in  rooms  having  hard  wood  floors  and  special  furnish- 
ings they  are  not  usually  permitted.  In  such  cases  the  floor- 
ivall  register  may  be  used  as  in  Fig.  31  6.  This  type  has  a  box 
and  leader  opening-  much  larger  than  is  possible  with  a  wall 
stack  and  compares  favorably  with  the  floor  type.  The  ap- 
pearance of  the  floor-wall  register  as  a  feature  of  the  room 
furnishings  and  its  sanitasy  qualities  are  enough  better  than 
the  floor  type  to  justify  its  general  use.  On  the  second  floor 
a  stack  is  necessary  and  the  wall  register  is  generally  used 
(Fig.  31  c).  Where  these  are  installed  the  upper  end  of  the 
stack  should  terminate  in  a  quarter  turn  to  throw  the  warm 
air  toward  the  room  and  avoid  eddy  currents  at  the  dead  end. 
All  intake  registers  to  the  rooms  and  vent  registers 
leading  to  the  attic  should  be  provided  with  shutters.  Re- 
turn lines  may  have  register  faces  only.  For  large  register 
faces  where  strength  is  not  an  important  factor,  grilles 
made  from  latticed  wood  strips  are  fre- 
quently used.  Fig-.  31  d  shows  one  of  these 
under  a  hall  seat.  For  calculations  and 
sizes  of  registers  see  Arts.  53-55,  and 
Tables  19  and  21,  Appendix. 

71.  Stacks  or  Risers: — The  vertical  air 
pipes  leading-  to  the  registers  are  called 
.s/^rA-.s  or  risers.  They  are  rectangular  in 
section  and  are  usually  fitted  within  the 
wall  (See  Fig.  32).  The  size  of  the  stud- 
ding and  the  distances  these  are  set,  cen- 
ter to  center,  limit  the  effective  area  of 
the  stack.  All  stacks  should  be  insulated 
to  protect  the  woodwork.  This  is  done  by 
making  the  stack  small  enough  to  clear 
the  woodwork  by  at  least  ^-inch  and  then 
wrapping  it  with  some  nonconducting  ma- 
terial such  as  asbestos  paper  or  hair  felt 
held  in  place  by  wire.  Patented  double 
walled  stacks  having  an  insulating  air  space 
between  the  walls  are  more  nearly  fire- 
proof. All  stacks  should  have  tight  joints  and  should  have 
ears  or  flaps  for  fastening  to  the  studding.  Patented  stacks 
are  made  in  standard  sizes  and  of  various  lengths.  Sizes  or- 
dinarily used  in  practice  are  given  in  Table  17,  Appendix. 


FURNACE    HEATING  111 

A  stack  is  sometimes  run  up  in  a  corner  or  in  some  re- 
cess in  the  wall  of  a  room  where  its  appearance,  after  being 
finished  in  color  to  compare  with  that  of  the  room,  is  not 
unsig-htly.  This  is  necessary  in  any  case  where  the  stack 
is  installed  after  the  building"  is  finished.  It  is  also  pre- 
ferred by  some  because  of  its  additional  safety  and  because 
more  stack  area  may  be  obtained  than  is  possible  when 
placed  within  a  thin  wall. 

All  stacks  should  be  located  in  or  near  partition  walls 
looking  toward  the  outside  or  cold  side  of  the  room.  This 
location  protects  the  air  current  from  excessive  loss  of  heat, 
as  would  be  the  case  if  placed  in  the  outside  walls.  It  also 
provides  a  more  uniform  distribution  of  the  air  from  the 
furnace. 

The  area  of  the  stack  best  adapted  to  any  given  room 
should  not  be  taken  by  guess  (See  Art.  56).  In  a  great 
many  cases  the  architect  specifies  light  partition  walls  be- 
tween large  upper  rooms,  say  4-inch  studding  set  16-inch 
centers  between  12-foot  by  15-foot  rooms,  heavily  exposed. 
From  the  theoretical  calculations  of  heat  losses,  these  rooms 
require  larger  stacks  than  can  be  placed  between  studding 
as  stated,  but  it  is  very  common  to  find  such  rooms  provided 
for  in  this  way.  One  possible  excuse  for  such  practice  may 
be  the  fact  that  most  second  floor  residence  rooms  are  de- 
signed for  sleeping  rooms  and  not  for  living  rooms.  Regard- 
less of  this  fact,  however,  it  would  be  well  to  provide  for 
all  emergencies  and  follow  the  rule  that  every  room  should  be 
provided  with  facilities  for  heat  as  if  it  icere  to  be  used  as  a  living 
room  in  the  coldest  weather.  If  this  were  done  there  would  be 
fewer  complaints  of  defective  heating  plants  and  less  mi- 
grating from  one  side  of  the  house  to  the  other  on  cold  days. 

Lack  of  heating  capacity  for  any  one  room  may  be  over- 
come by  providing  two  stacks  and  registers  instead  of  one. 
This  plan  will  be  fairly  satisfactory  since  one  of  the  regis- 
ters may  be  shut  off  in  moderate  weather.  It  requires  an 
additional  expense,  however,  which  is  not  justified.  A  better 
way  is  to  provide  partition  walls  of  greater  thicjkness  or 
specially  planned-for  stack  openings,  so  that  ample  stack 
area  may  be  put  in.  The  ideal  conditions  will  be  reached 
when  the  architect  anticipates  the  heating  requirements  and 
provides  air  shafts  of  sufficient  size  to  accommodate  round 
or  nearly  square  stacks. 


112 


HEATING  AND   VENTILATION 


Single  stacks  are  sometimes  used  to  supply  air  to  two 
adjoining  rooms.  Such  stacks  have  metal  partitions  extend- 
ing down  a  few  feet  from  the  upper  end  to  split  the  air  cur- 
rent and  direct  it  to  the  rooms.  This  practice  is  question- 
able because  of  the  liability  of  the  pressure  of  air  in  the 
room  on  the  cold  side  of  the  house  forcing  the  heated  air 
around  the  partition  to  the  other  room.  Also,  single  stacks 
are  frequently  used  to  supply  rooms  one  above  the  other. 
This  is  not  satisfactory  except  where  the  regulation  in  each 
room  is  taken  care  of  by  the  same  person.  When  the  upper 
register  is  full  open  it  will  rob  the  lower  register  and  when 
the  lower  damper  is  full  open  the  upper  room  gets  no  heat. 
A  better  method  is  to  install  a  separate  line  for  each  room  to 
be  heated. 

Vent  stacks  should  be  located  in  the  inner  or  partition 
walls  and  should  lead  to  the  attic.  If  it  is  thought  neces- 
sary, they  may  there  be  gathered  together  in  one  duct  lead- 
ing to  a  vent  through  the  roof.  It  is  an  ideal  arrangement 
but  not  always  necessary  to  have  a  vent  stack  in  every 
room.  Some  rooms,  from  their  location,  are  easily  ventilated 
without  them.  Bath  rooms,  toilets,  laundries  and  kitchens,  and 
rooms  near  the  center  of  the  house  should  always  have  independent 
rt'ntilalion.  In  any  rooms  where  nat- 
ural  ventilation  is  an  important  fea- 
ture, vent  ducts  to  the  attic  should 
have  two  tappings,  floor  and  ceiling, 
each  provided  with  shuttered  regis- 
ters. The  floor  vent  should  be  used 
on  cold  days  to  economize  the  heat 
and  the  ceiling  ven-t  should  be  used 
on  warm  days.  Such  a  system  of 
ventilation  may  be  used  in  connec- 
tion with  direct-indirect  radiators  in 
Fig.  33.  small  schools  (See  Fig.  33). 

72.  Air  Circulation  Within  the  Room: — The  location  of 
the  heat  register  relative  to  the  vent  register,  will  determine 
to  a  great  extent  the  circulation  of  air  within  the  room. 
Fig.  34  a,  6,  c,  and  a,  shows  the  effect  of  the  different  loca- 
tions in  forced  circulation.  The  best  plan,  from  the  stand- 
point of  heating,  is  to  enter  the  air  at  a  point  above  the 
heads  of  the  occupants  and  withdraw  it  from  the  floor  line, 
at  or  near  the  same  side  from  which  the  air  enters.  This 


FURNACE   HEATING 


113 


(d) 


gives  a  more  uniform  distribution  as  shown  by  the  last 
figure.  It  is  doubtful,  however,  if  this  method  will  give  the 
best  ventilation  in  crowded  rooms  where  the  foul  air  nat- 
urally collects  at  the  top  of  the  room.  Circulation  in  fur- 
nace heating  is  not  as  satisfactory  as  in  other  forms  of  in- 
direct heating.  Air  usually  enters  the  room  from  the  floor 
or  the  inner  wall  near  the  floor  line  and  leaves  for  recircula- 
tion  near  the  floor  line  on  the  opposite  or  cold  side.  Circula- 
tion within  the  room  is  shown  by  &.  Where  there  is  no  re- 
circulation  it  leaves  through  a  vent  register  usually  near 
the  floor  line  and  located  at  such  a  point  that  the  air  will 
traverse  as  much  of  the  room  as  possible  before  leaving. 

7.-S.  Pan-Furnace  Heating  System: — In  large  furnace  in- 
stallations where  the  air  is  carried  in  long  ducts  that  are 
nearly,  if  not  quite  horizontal  and  where  a  positive  supply 
of  air  is  a  necessity  in  all  parts  of  the  building,  a  combina- 
tion fan  and  furnace  system  may  be  installed.  Such  sy»- 
tems  may  be  properly  designated  mechanical  warm  air  sys- 
tems but  they  should  not  be  confused  with  the  mechanical 
fan-coil  systems  described  in  Chapters  ~K  to  XII.  The  objec- 
tions urged  against  the  fan-furnace  systems  are  the  high 
temperatures  of  the  circulating  air  and  the  smoke  and  dust 
content  picked  up  from  the  furnace. 

Fan-furnace  systems  may  be  set  in  multiple  if  desired, 
i.  e.,  one  fan  operating  in  connection  with  two  or  more  fur- 


114 


HEATING  AND   VENTILATION 


naces.  Fig.  35  represents  a  two-furnace  plant  showing  a 
fan  and  two  furnaces.  Air  is  drawn  into  the  fresh  air  room 
through  a  grate  in  the  outside  wall  and  is  forced  through 
the  fan.  to  the  furnaces  where  it  divides  and  passes  up 
through  each  furnace  to  the  warm  air  ducts.  Part  of  the 
fresh  air  from  the  fan  is  by-passed  over  the  top  of  the  fur- 
naces and  is  admitted  to  the  warm  air  ducts  through  mixing 


Fig.  35. 

dampers.  These  dampers  control  the  amount  of  hot  and  cold 
air  for  any  desired  temperature  of  the  mixture.  Temperature 
control  may  be  installed  and  operated  with  this  system. 
Paddle  wheel  fans  (always  located  between  the  furnace  and 
air  intake)  are  preferred,  although  the  disk  wheel  may  be 
used  where  the  pipes  are  -large  and  where  the  air  must  be 


FURNACE   HEATING 


115 


carried  but  short  distances.  For  fan  types  see  Chapter  X. 
74.  Hot  Air  Radiator  Systems: — In  some  localities  gas, 
either  natural  or  manufactured,  is  used  as  fuel  for  heating 
purposes.  Wherever  the  supply  is  available  at  rates  com- 
mercially reasonable,  it  may  be  piped  direct  to  radiators 
within  the  rooms  and  burned  as  in  ordinary  gas  stoves,  the 
products  of  combustion  being  circulated  through  the  radia- 
tors and  then  exhausted.  This  is  the  principle  of  the  Rector 
system  (Fig.  36).  The  gas  supply  to  each  burner  is  under 
double  control:  first,  by  a  thermostat  which  maintains  con- 
stant room  temperature;  second,  by  vacuum  produced  by  the 
exhaust  fan  which  acts  as  a  safety  appliance.  For  thermo- 


Fig.  36. 

static  control  see  Chapter  XIV.  For  vacuum  control,  a  valve 
in  each  radiator  is  so  arranged  that  when  the  vacuum  fails, 
due  to  the  stopping  of  the  fan,  gas  is  shut  off  from  the  bur- 
ner, leaving  only  a  pilot  light  flame.  When  the  vacuum  is 
again  produced  by  the  starting  of  the  fan,  gas  is  admitted 
to  the  burner  and  ignited  automatically  by  the  pilot  light. 
The  products  of  combustion  pass  upward  to  the  top  and  then 
downward  through  the  sections  where  they  are  drawn  off  from 
the  bottom  central  connection  by  the  exhaust  fan.  No  water, 
steam  or  circulating  mediums  other  than  the  combustion 
products  themselves,  are  used.  The  facts  that  combustion 


116 


HEATING  AND  VENTILATION 


takes  place  within  the  room  to  be  heated,  that  the  only  loss 
of  heat  is  that  carried  off  by  the  exhausting  gases  and  that 
each  room  is  an  independent  unit  give  just  claim  for  high 
efficiency  in  fuel  economy.  Such  a  system  is  practically 
under  the  control  of  a  push  button  which  starts  and  stops 
the  motor  exhaust  fan.  It  is  very  convenient  with  its  flexi- 
bility and  independence  of  units  and  is  conducive  to  economy 
under  careful  management.  The  calculated  radiator  sur- 
face is  less  than  that  required  for  steam  systems,  because 
of  the  higher  average  internal  temperature. 

Gas  radiators  should  not  be  placed  close  to  woodwork  or 
other  inflammable  material.  In  general,  advantages  such  as 
no  janitor  service,  no  coal  storage  spaces,  no  furnace  chim- 
ney, no  coal  dust  and  dirt,  and  no  ashes  are  inherent  with 
these  systems.  They  are  used  in  localities  having  mild 
climates  and  where  continuous  firing  is  not  necessary. 

-In  the  Haivkes  system  the  exhaust  fan  and  the  automatic 
gas  valve  of  the  Rector  system  are  eliminated.  The  products 
of  combustion  pass  through  radiators  similar  to  those  just 


Fig.  37.  Fig.  38. 

mentioned  but  the  exhausting  of  these  products  is  accom- 
plished by  connecting  each  radiator  to  a  stack,  or  by  provid- 
ing a  separate  2-inch  riser  to  the  roof  which  acts  as  a  stack 
for  that  particular  radiator.  The  air  necessary  for  burning 
the  gas  is  admitted  through  slots  near  the  bottom  of  each 
section  of  the  radiator.  All  radiators  are  operated  by  hand 
control  in  the  same  way  as  the  ordinary  gas  stove.  Fig.  37 
shows  the  Hawkes  ventilating  gas  radiator  as  commonly 
installed. 


FURNACE   HEATING 


117 


Hot  air  radiators  heated  by  gas  may  also  be  of  the  in- 
direct type  in  which  case  they  are  designated  gas  floor  fur- 
naces. Fig-.  38  shows  one  of  these  furnaces  connected  to  a 
first  floor  register.  The  operation  is  like  that  of  the  pipeless 
furnace,  Art.  65.  Above  the  furnace  is  a  combination  hot- 
and-cold  air  register  which  recirculates  the  room  air  over  a 
gas  heated  cast  radiator.  Combustion  takes  place  within 
the  cast  radiator  and  the  gases  are  carried  by  vent  pipes  to 
the  chimney.  These  furnaces  are  hand  controlled  at  the 
register. 

75.  Fire  Hazard:  —  Protection  against  fire  from  heating 
apparatus  is  too  little  considered  by  the  average  house- 
holder. Several  points  in  every  furnace  plant  may  be  con- 
sidered danger  points.  These  are,  in  the  order  of  impor- 
tance: a  loosely  built  chimney,  the  top  of  the  chimney  too 
close  to  a  steep  pitched  shingle  roof,  wood  work  of  the 
house  fixed  rigidly  to  the  chimney,  the  smoke  pipe  from  the 
furnace  too  close  to  the  house  framing,  the  top  of  the  fur- 
nace unprotected  and  too  close  to  the  joists  or  basement 
ceiling,  and  the  hot  air  pipes  too  close  to  the  wood  work. 
Especial  care  should  be  taken  in  protecting  gas  floor-heaters, 
as  described  in  Art.  74.  The  ounce  of  prevention  in  such 
cases  may  be  easily  and  cheaply  applied,  and  should  be  in- 
sisted upon. 

78.  Accelerating  Circulation  in  Furnace  Plants:  —  Many 
furnace  plants  are  not  giving  satisfaction  because  of  slug- 

gish circulation.  This  trouble 
which  in  most  cases  may  be 
traced  to  defective  design,  may 
be  corrected  as  in  Fig.  39,  by 
inserting  a  12-  to  16-inch  disk 
fan  in  the  return  duct,  prefer- 
ably below  the  inlet  point  of  the 
outside  air.  The  fan  may  be 
run  when  warming  up  the  house 
in  the  mornings  and  at  times  of 
severe  weather.  This  may  be 
connected  to  the  average  lamp 
socket  and  will  cost  from  %  to 
1  cent  per  hour  depending  upon 


li 

V- 

j  * 

1 

1 

ft 

CE 

|                         > 

1 

i 

§ 

H  RfDUC  f  R 

n  I 

TO  r«/RN/\ 

p. 


the  electric  prices  in  the  locality. 


118  HEATING  AND  VENTILATION 

77.  Suggestions  for  Operating:  Furnaces: — Furnaces  are 
designated  hard  coal  and  soft  coal,  depending-  upon  the  type  of 
design  and  the  construction  of  the  grate,  hence  the  grade  of 
coal  best  adapted  to  the  furnace  should  be  used.  The  size 
of  the  openings  in  the  grate  should  determine  the  size  of 
coal  used. 

Keep  coal  in  coal  pile  moist  but  not  wet. 

Clean  all  furnace  gas  passages  frequently. 

Keep  the  fire  pot  well  filled  with  coal  and  have  it  evenly 
distributed  over  the  grate,  firing  light  arid  often  for  best 
service.  In  a  properly  designed  plant,  when  necessary,  fir- 
ings may  be  as  few  as  three  or  four  per  24  hours  and  give 
good  service. 

Keep  the  fire  free  from  clinkers.  They  should  be  re- 
moved from  the  fire  once  or  twice  daily.  It  is  not  necessary 
to  stir  the  fire  so  completely  as  to  waste  the  coal  through 
the  grate.  With  a  good  chimney  draft,  some  ashes  just 
above  the  grate  line  will  be  a  benefit  in  that  it  will  retard 
the  fire  and  tend  toward  less  clinkering.  Clinkers  are  formed 
with  high  volatile  coals  and  strong  draft  through  the  grate. 
They  are  avoided  by  slow  and  steady  combustion,  by  having  a  thick 
fuel  bed  of  live  coals  and  by  having  sloiv  draft  through  the  grate 
(generally  draft  damper  fully  closed  and  small  draft  above  the  fire). 
The  arrangement  of  these  dampers  will  be  determined  by 
experience. 

A  good  sized  chunk  of  wood  embedded  into  the  top  of 
the  fuel  bed  is  a  coal  saver. 

When  replenishing  a  poor  fire  do  not  shake  the  fire,  but 
put  on  some  coal  (or  chunk  of  wood)  and  open  the  drafts. 
After  the  fuel  is  well  ignited  clean  the  fire. 

The  ash  pit  should  be  cleaned  each  day.  An  accumula- 
tion of  ashes  below  the  grate  soon  warps  the  grate  and 
burns  it  out.  Sifting  shovels  may  be  used  and  the  unburned 
coal  put  back  in  the  furnace. 

Keep  all  dampers  in  working  order. 

Have  a  hand  damper  in  the  smoke  pipe  and  keep  it  open 
only  as  far  as  is  necessary  to  create  a  draft.  Check  damper 
(opening  to  basement  air)  must  not  be  open  unless  draft 
damper  under  grate  is  closed. 

Keep  the  water  pans  full  of  water  and  all  humidity 
apparatus  working1. 

Clean  the  base  of  the  chimney,  the  furnace  and  the 
smoke  pipe  thoroughly  in  all  parts  at  least  once  each  year. 


FURNACE   HEATING  119 

Keep  the  fresh  air  duct  free  from  rubbish  and  impurities. 

Allow  plenty  of  pure  fresh  air  to  circulate  through  the 
furnace.  In  cold  weather  part  of  this  supply  may  be  cut  off. 
When  fuel  saving1  is  a  necessity,  it  may  be  cut  off  entirely. 

Have  the  basement  well  ventilated  by  means  of  outside 
wall  ventilators,  or  by  special  ducts  leading  to  the  attic. 
Never  permit  the  basement  air  to  be  circulated  to  the  living 
rooms. 

To  bank  the  fires  for  the  night,  shake  down  and  clean 
the  fire,  bank  the  live  coals  to  one  side  of  the  fire  box,  fill  up 
with  fresh  fuel,  sift  the  ashes  and  distribute  the  unburned 
coal  on  the  fire;  with  a  poker  make  a  hole  through  the  fill 
into  the  live  coal  bed  to  permit  of  some  flame  above  the  fuel 
bed,  close  the  under  drafts  and  open  the  fire  door  draft 
slightly.  Caution. — Never  cover  the  entire  incandescent  fuel  bed 
with  fresh  coal  and  close  the  drafts.  If  this  is  done,  coal  gas 
will  collect  above  the  fire  and  will  ignite  from  the  first  flame 
that  breaks  through  the  fuel  bed,  causing  an  explosion. 


CHAPTER  VI. 


HOT    WATER   AND    STEAM    HEATING. 

DESCRIPTION   AND   CLASSIFICATION. 

78.  Hot     Water     and     Steam     Systems     Compared     with 
Furnace    Systems:— Hot    water    and    steam    installations    are 
more   complicated    in   the   number   of  parts   than   furnace    in- 
stallations;   they    use    a    more    cumbersome    heat    carrying 
medium,  for  which  a  return  path  to  the  boiler  must  be  pro- 
vided;   and    have    parts,    in    the    form    of    radiators,    which 
occupy  valuable  room  space.     But  the  hot  water  and  steam 
plants  have  the   advantage   in   that  the  circulation,   and   the 
transference    of   heat,    are    not    affected    by    wind    pressures. 
Hot  water  and  steam  will  carry  heat  as  readily  to  the  wind- 
ward side  of  a  house  as  to  the  leeward   side,  a  point  which 
is  known  to  be  quite   impossible  with  air.     Furnace  heating 
has    the    advantage    of    inherent    ventilation,    while    the    hot 
water   and   steam   systems,   as   usually   installed,    provide   no 
ventilation  except  that  due  to  air  leakage. 

79.  Elements   of   Hot    Water   and    Steam    Systems: — Hot 
water   and   steam   systems   consist   of   three    principal   parts: 
the   boiler   or  heat   generator,   the   radiators   or   heat   distrib- 
utors,  and   the   connecting  pipe   lines   which   provide   the  cir- 
cuit paths  for  the  hot  water  or  the  steam.     In  the  hot  water 
system  it  is  essential  that  the  heat  generator  be  located  at 
the   lowest  point   in   the   circuit  for,   as  explained   in  Art.   11, 
the  only  motive  force   is  that  due  to  convection  currents  in 
the  water.      In   the  steam   system   this   is   not  essential.      The 
water    of    condensation    may    or    may    not    be    returned    by 
gravity  to  the  boiler.     Hence,  with  a  steam  system  a  radia- 
tor may  be. placed   below   the   boiler,   if   its  condensation  be 
trapped  or  otherwise  taken  care  of. 

Concerning  piping  systems  and  connections,  several 
terms  commonly  used  by  heating  engineers  should  be  de- 
fined. The  large  pipes  in  the  basement  connected  directly 
to  the  source  of  heat,  and  serving  as  feeders  to  the  pipes 
running  vertically  in  the  building,  are  known  as  wains. 
Supply  mains  are  those  that  carry  water  or  steam  from  the 
source  of  heat  to  the  radiators  and  return  mains  are  those 


HOT  WATER  AND   STEAM   HEATING 


121 


that  carry  water  or  condensation  from  the  radiators  to  the 
source  of  heat.  The  vertical  pipes  connecting  between  floors 
are  called  risers,  while  the  short  horizontal  pipes  between 
risers  and  radiators  are  riser  arms  or  branches.  As  there  are 
supply  mains  and  return  mains,  so  also  there  are  supply 
risers  and  return  risers.  A  return  main  traversing  the 
basement  above  the  water  line  of  the  boiler  is  designated  a 
dry  return  and  carries  both  steam  and  water  of  condensation; 
one  in  such  position  below  the  water  line  as  to  be  filled  with 
water  is  designated  a  wet  return.  The  returns  of  all  two- 
pipe  radiators  connecting  with  wet  returns  are  said  to  be 
sealed. 

80.  Classifications: — One  classification  of  hot  water  and 
steam  systems  is  based  upon  the  position  and  manner  in 
which  the  radiators  are  used.  The  arrangement  which  is 
most  familiar  is  the  one  wherein  the  radiators  are  located 
within  the  space  to  be  heated  and  are  surrounded  only  by 
room  air.  Radiators  so  placed  (Fig.  40)  provide  no  ven- 
tilation and  are  designated  direct  radiation.  In  direct-indirect 


Fig.  40. 


Fig.  41. 


radiation  the  radiators  are  placed  as  in  direct  radiation  but 
the  lower  portion  of  each  radiator  is  encased  and  connected 
with  the  outside  air  as  shown  by  Fig.  41.  The  direct-indirect 
system  provides  certain  ventilating  possibilities  and  should 
always  be  used  in  connection  with  inside  wall  ventilating 
stacks.  Indirect  radiation  is  installed  remote  from  the  rooms 


HEATING   AND   VENTILATION 

ROOM    HEATED 


to  be  heated  and  ducts  carry  the  heated  air  from  the  radia- 
tors to  the  rooms  either  by  convection,  or  by  fan  or  blower 
pressure.  In  residence  work  this  radiation  is  usually  sus- 
pended from  the  basement  ceiling  as  shown  by  Fig.  42.  This 


Fig.  43. 


HOT   WATER  AND   STEAM   HEATING  123 

provides  a  combination  system  of  steam  and  indirect  warm 
air.  When  the  radiation  for  an  entire  building-  is  installed 
in  one  basement  room,  and  each  room  of  the  building  has 
carried  to  it  its  share  of  heat  by  forced  air  through  ducts 
from  one  large  centralized  fan  or  blower,  the  system  is 
called  a  plenum  system  or  fan-coil  system  and  is  given  special 
consideration  in  Chapters  X  to  XII. 

A  second  classification  for  hot  water  and  steam  systems  is 
made  according  to  the  method  of  pipe  connection  between 
the  heat  generator  and  the  radiation.  The  one-pipe  basement 
main  steam  system  (Fig.  43)  is  the  simplest  in  construction 
and  is  preferred  by  many  for  steam  installations.  As  the 
name  indicates,  its  distinguishing  feature  is  the  single  pipe 
path  leading-  from  the  source  of  heat  to  the  radiator,  the 
steam  and  the  returning  condensation  both  using  this  path. 
In  the  risers  and  connections  the  steam  and  condensation 
flow  in  opposite  directions,  thus  requiring  larger  pipes  than 
where  a  flow  and  a  return  are  both  provided.  In  the  mains 
the  condensation  usually  flows  with  the  steam  and  not 
against  it.  In  the  so-called  one-pipe  basement  main  hot  water 
system  (Fig.  49),  radiators  have  two  tappings  and  two  risers, 
but  the  flow  riser  is  tapped  out  of  the  top  of  the  single 
basement  main,  while  the  return  riser  is  tapped  into  the  bot- 
tom of  that  same  main  by  either  of  the  special  fittings  shown 
in  section  in  Fig.  44.  The  theory  is  that  the  hot  water  from 
the  boiler  travels  along  the  top  of  the 
main,  while  the  cooler  water  from  the 
radiators  travels  along  the  bottom  of 
this  same  main  and  two  streams  re- 
main separate.  Where  mains  are  short 
and  straight  as  in  small  residence  in- 
stallations, this  system  seems  to  give 
satisfaction,  but  where  mains  are  long 
and  more  complicated  a  mixing1  of  the 
,,,.  4  two  streams  is  unavoidable  and  the 

supply     to     the     farther     radiators     is 
cooled  to  such  a  degree  that  the  system  becomes  unreliable. 

The  two-pipe  basement  main  system  (Figs.  47  and  50)  is 
standard  with  both  steam  and  hot  water  installations.  For 
steam  work  (especially  for  small  installations)  it  is  prob- 
ably no  better  than  the  one-pipe  system  but  for  hot  water 
work  it  is  much  preferred.  In  this  system  two  separate  and 


124 


HEATING  AND  VENTILATION 


distinct  paths  may  be  traced  from  any  radiator  to  the  source 
of  heat.  In  the  basement  are  two  mains,  the  supply  and  the 
return,  and  the  risers  from  these  are  always  run  in  pairs, 
the  supply  riser  on  one  side  of  a  tier  of  radiators,  the  return 
riser  on  the  other  side.  A  two-pipe  steam  system  should 
have  sealed  returns  (See  Art.  82). 

The  attic  supply  system,  or  Mills  system,  has  found  much 
favor  with  heating  engineers  in  the  installation  of  the  larger 
steam  and  hot  water  plants.  In  this 
system  the  supply  and  returns  both 
flow  downward.  This  is  accomplished 
by  first  leading  the  steam  or  water  to 
the  attic  through  one  large  main  which 
there  branches  to  supply  the  various 
risers.  One  riser  only  is  generally  used 
for  each  tier  of  steam  radiators.  Fig.  45 
shows  one-  and  two-pipe  radiator  con- 
nections. Frequently  two-pipe  connec- 
tions are  made  to  a  single  riser  pipe. 
WThen  this  is  done  a  water  type  radi- 
ator must  be  used  with  the  supply  en- 
tering the  top  and  the  return  leaving 
the  bottom  of  the  same  side  (See  vapor 
heating  systems). 

.1   third  cldnxifirution  may  be  made,  hav- 
ing reference   to   the   manner  of  circu- 


Fig.  45. 


lating  the  heating  medium  and  to  its  pressure.  This  classifi- 
cation covers  a  multitude  of  inventions  upon  the  attachment 
of  which  increased  capacity  and  efficiency  are  claimed  over 
the  ordinary  gravity  systems.  In  outline,  this  classification 
may  be  stated  as  follows: 

Gravity  Systems 

Steam  systems,  circulating  steam  at  pressures 
greater  than  atmosphere. 

Water,  open  tank  systems,  circulating  water  by  in- 
creased weight  of  water  in  return  risers  over 
warm  water  in  supply  risers. 

Modified  Gravity  Systems 

Steam  systems,  circulating  steam  at  atmospheric 
pressure  or  below. 


HOT  WATER  AND   STEAM   HEATING  1125 

Water    systems,    circulating'    water    under    pressure, 
at    temperatures   above   those   possible   with    the 
open   tank   systems   and    with   accelerated   veloc- 
ities. 
Combination   steam    and  gas   systems   with    radiators   as 

heaters  independent  of  a  centralized  heat  supply. 
Systems  mentioned  in  this  classification  are  explained  in 
Arts.  81  to  85. 

GRAVITY     SYSTEMS. 

81.  Steam  and  Hot  Water  Systems: — Ordinary  low  pres- 
sure  steam    installations   operate   at   pressures   from    1   to   10 
pounds  gage.     Relief  valves  are  provided  which  release  the 
steam  when  pressures  tend  to   increase  above  the  set  maxi- 
mum  and   thus  protect   the  boiler   from   excessive  pressures. 
Pressures  in  the  boiler  are  maximum.     These  decrease  grad- 
ually along  the  circuit  of  the  supply  and   return  mains  be- 
cause of  the  frictional  retardation  of  the  circulating  steam, 
giving  a   pressure   drop   between   main   and   return   near   the 
boiler  of   V2   to  1  pound.     The  water  in  the  return,  therefore, 
stands  above   the  water  level   in   the  boiler  an  amount  suf- 
ficient   to    balance    this    differential    pressure.      All    pipes    in 
the    system    are    graded    for    easy    flow    of    the    condensation 
back  to  the  boiler.     Each  boiler  must  be  fitted  with  a  pres- 
sure gage,  a  safety  valve  or  pop  valve  and  a  draft  regulat- 
ing device.     Each  radiator  must  have  a  first-class  automatic 
air  valve. 

An  ordinary  hot  water  installation  has  an  open  expansion 
tank  at  the  highest  point  of  the  system  to  permit  change  in 
volume  in  the  water  as  it  changes  temperature,  such  systems 
operate  at  pressures  equivalent  only  to  the  static  head  of 
the  water  in  the  system.  Pressures  at  the  boiler  range  from 
15  to  25  pounds  gage  for  residence  work.  Water  tempera- 
tures above  212°,  therefore,  will  cause  a  loss  of  steam  out 
the  overflow  of  the  expansion  tank  and  are  not  considered 
advisable.  Each  boiler  is  fitted  with  a  pressure  gage  or  alti- 
tude gage  to  show  the  height  of  water  in  the  expansion  tank, 
a  thermometer  to  show  the  temperature  of  the  circulating 
water  and  a  draft  regulating  device.  Each  radiator  must 
have  a  compression  air  cock. 

82.  Diagrams  for  Gravity  Steam  and  Hot  Water  Piping: 
Systems: — Figs.  46  to  51  inclusive  show  some  of  the  methods 
of  connecting  up  piping  systems  between  the  source  of  heat 
and   the   radiators.     A,   B,   C   and   D   show   different   methods 


126 


HEATING  AND   VENTILATION 


ONE    PIPE   STEAM    SYSTEM -BASEMENT     MAIN 


Fig.  46. 


TWO    PIPE   STEAM    SYSTEM-BASEMENT    MAIN 


Fig".  4' 


HOT   WATER   AND   STEAM   HEATING  127 


Fig".  48. 


ONE     PIPE.    'SYSTEM-HOT    WATER 


Fig.  49. 


128 


HEATING  AND  VENTILATION 


TWO    PIPE.    SYSTEM    HOT  WATER -BASE  ME  NT     MAIN 


a 

i 

At 

aa 

4 

C3Q 

Fig.  50. 

of  connecting-  between  the  radiators  and  mains.  The 
branches  below  the  floor  and  behind  the  radiators  are  for 
the  purpose  of  taking  up  expansion.  Short  connections 
should  be  avoided.  It  will  be  noticed  that  the  two-pipe 
steam  systems  have  sealed  returns  where  they  enter  the 
main  return  above  the  water  line  of  the  boiler.  Dry  returns 
frequently  interfere  with  the  circulation  of  the  steam  to  the 
radiators  by  short-circuiting.  Steam  from  the  boiler  follows 
the  path  of  least  resistance  to  each  radiator  and  many  times 
this  path  leads  up  the  return  line  into  the  radiator  instead 
of  through  the  supply.  In  Fig.  47  suppose  the  radiators  C 
and  D  increased  in  number  to  the  right  C',  D',  C",  D",  etc., 
and  all  connected  to  the  main  as  shown  and  to  the  return 
without  the  loop.  It  is  easy  to  see  that  steam  from  the 
supply  main  would  flow  through  the  radiators  C  and  D  into 
the  dry  return  where  it  would  continue  to  the  end  of  the 
line  and  affect  the  easy  flow  of  steam  through  the  end  radia- 
tors. If  the  main  inlet  to  any  radiator  were  restricted,  the 
steam  to  that  radiator  would  be  supplied  through  its  return 
branch  thus  blocking  circulation  and  causing  ic<ttcr-Ji<i>ni>i<T. 
The  only  way  to  insure  against  this  is  to  water-seal  each  re- 
turn by  connecting  as  shown  or  by  connecting  to  a  wet  re- 
turn. 


HOT  WATER   AND   STEAM   HEATING 


Fig.  51. 

Hot  water  gravity  circulation  is  more  easily  retarded 
than  steam  circulation  and  greater  care  must  be  exercised  in 
laying  out  and  installing  the  systems.  Fig.  50  shows  the 
connections  most  frequently  used  with  basement  mains. 
Connections  recommended  for  the  Mills  overhead  hot  water 
system  are  shown  in  Fig.  51.  Where  all  radiators  in  the 
same  tier  are  connected  flow  and  return  to  the  same  drop 
riser,  circulation  is  frequently  equalized  in  the  radiators 
by  O.  S.  Distributors  turned  against  the 
stream  in  the  supply  and  with  the 
stream  in  the  return  (See  Fig.  52). 

Basement  radiation  usually  has  poor 
circulation.  In  steam  systems  if  the 
water  of  condensation  is  to  be  returned 
to  the  boiler  it  is  placed  on  the  ceiling 
or  wall  as  high  above  the  water  line  as 
possible.  If  the  water  is  to  be  trapped 
to  the  sewer  it  may  be  placed  on  the 
floor.  Hot  water  radiation  may  be  placed  at  any  elevation 
above  (not  below)  the  return  inlet  to  the  boiler.  Circulation 
is  improved,  however,  if  the  radiator  supply  is  connected 


Fig.  52. 


130 


HEATING   AND   VENTILATION 


Fig".  53. 


from  some  point  above  the  basement.  Fig.  53  shows  such 
connections.  Increasing  the  drop  increases  the  rate  of  cir- 
culation. 


MODIFIED   GRAVITY    SYSTEMS. 

83.  Atmospheric  and  Vapor  Systems: — Low  pressure 
steam  systems  are  not  as  well  adapted  as  hot  water  systems 
for  moderate  service,  say  on  spring  and  fall  days  when  only 
a  small  percentage  of  the  full  capacity  of  the  heating-  system 
is  required.  Difficulty  is  experienced  in  keeping  uniform 
temperature  conditions  in  the  radiators.  In  small  plants, 
such  as  are  found  in  residences  where  a  constant  attendant 
can  not  be  provided,  temperatures  alternate  rapidly  between 
maximum  and  minimum.  In  an  endeavor  to  meet  the  de- 
mand for  a  steam  system  which  will  serve  for  all  outside 
weather  conditions,  a  number  of  modified  low-pressure 
steam  systems,  called  vacuum,  vacuo-vapor,  vapor,  modula- 
tion or  atmospheric  systems  have  been  devised.  It  is  claimed 
for  these  systems  that  they  give  better  regulation  and  more 
uniform  temperature  conditions,  also  that  they  are  free  from 
air  troubles. 

The  term  vacuum  should  properly  not  be  applied  to  this 
class  but  should  belong  to  those  systems  having  a  positive 
vacuum  in  the  returns  mechanically  produced  by  action  of 


HOT  WATER  AND   STEAM  HEATING 


131 


pumps,  ejectors,  etc.,  as  explained  in  Chapter  IX.  There  is 
one  gravity  system,  however,  that  has  some  claim  to  the 
name — the  Mercury  Seal  Vacuum  System.  Fig.  54  represents  the 
outer  coils  of  any  radiator.  Inside  the  last  coil 
is  a  mercury  pot  with  a  vertical  iron  tube  con- 
nection for  mercury  column  similar  to  the  aver- 
age barometer.  The  top  of  this  tube  is  connected 
with  the  atmospheric  side  of  the  automatic  air 
valve.  When  not  in  service  the  mercury  in  the 
column  drops  to  the  pot.  When  firing-  up,  the  air 
valve  permits  the  escape  of  air  but  closes 
against  steam.  The  mercury  pot  freely  allows 
the  escape  of  this  air  but  does  not  permit  its 
return.  As  a  result  the  heating  system  (any 
kind  of  system)  warms  up  and  expels  the  air 
but  when  it  cools  down  a  partial  vacuum  is  es- 
tablished and  the  water  continues  to  boil  at  tem- 
peratures below  212°.  If  the  system  of  piping 
and  valves  is  very  tight  a  partial  vacuum  may 
be  maintained  throughout  the  night,  during 
which  time  steam  will  circulate  at  low  pressure 
until  the  temperature  falls  say  as  low  as  150°. 
Further  it  will  heat  up  more  quickly  and  with 
less  fuel  in  the  morning  because  of  this  partial 
vacuum.  To  have  a  mercury  column  at  each  radi- 
ator would  be  prohibitive  because  of  the  expense, 
consequently  where  this  system  is  used  the  air 
lines  are  run  to  the  basement  in  a  similar 


e[ 


Fig.  54. 


way  to  those  of  the  returns,  collected  together  and  attached 
to  a  mercury  seal  of  sufficient  size  to  expel  the  air  from 
the  entire  heating  system.  Such  a  system  is  sometimes 
called  an  air-line  system.  The  above  arrangement  is  very  de- 
sirable and  is  in  sharp  contrast  to  the  ordinary  system 
where  the  steam  leaves  the  radiators  as  soon  as  the  tem- 
perature falls  below  212°.  The  practical  difficulties  in  ob- 
taining and  maintaining  an  air  tight  piping  system,  however, 
limits  its  use. 

The  terms  vapor,  vacuo-vapor,  modulation,  atmospheric  and 
the  like  are  trade  terms  that  are  not  especially  distinctive 
but  which  indicate  all  the  large  number  of  gravity  steam 
systems  operating  at  pressures  from  0 —  to  1 —  pound  gage. 
In  these  systems  the  radiators  are  water-type,  two-pipe, 


132  HEATING   AND   VENTILATION 

top  connected  and  have  packless  valves  and  no  air  valves. 
Steam  being  lighter  than  air  it  first  fills  the  top  of  the 
radiators  and  gradually  forces  the  air  downward  and  out 
the  return  to  the  atmosphere.  The  radiator  outlet  is  usually 
on  the  opposite  side  of  the  radiator  from  the  inlet,  water  of 
condensation  and  air  both  passing  through  this  opening. 

The  important  feature  in  operating  any  gravity  heating 
system  at  pressures  near  atmosphere  and  especially  those 
having  no  automatic  control  on  the  air  relief,  is  effective 
regulation.  Where  this  is  obtained  there  will  be  fairly  uni- 
form temperature  conditions  within  the  radiator,  sufficient 
heat  emission  to  satisfy  the  room  requirements,  and  no 
wastage  of  steam.  Regulation  may  be  applied  at  any  of 
the  four  points  in  the  system — at  the  boiler,  in  which  case 
the  drafts  are  controlled  by  a  hydraulic  head,  a  float  located 
in  a  receiver  at  the  end  of  the  return  main  or  by  a  pressure 
regulator  connected  to  the  steam  space  of  the  boiler — at  the 
inlet  valve  to  the  radiator — at  the  radiator  outlet — and  at 
the  atmospheric  vent  at  the  end  of  the  return  main.  All 
systems  of  this  kind  have  automatic  draft  regulation  and  all 
have  radiator  inlet  valves  that  give  more  or  less  satisfac- 
tory hand  or  thermostatic  control.  The  essential  differences 
in  the  various  types,  therefore,  lie  in  the  character  of  the 
regulation  at  the  radiator  outlets  and  at  the  air  relief  on  the 
end  of  the  return  main.  Classifying  the  many  systems  on 
the  market,  a  few  only  of  which  will  be  mentioned,  they 
may  be  grouped  under  three  general  heads. 

Type  1,  Fig.  55,  has  no  positive  regulation  on  the  radia- 
tor outlets  or  on  the  air  relief.  (A  thin  water  seal  is  here 
considered  as  no  regulation  since  in  every  case  a  positive 
vent  opening  is  provided  for  air).  In  estimating  radiation 
for  this  type,  20  per  cent,  more  is  put  in  than  would  be  re- 
quired for  any  low  pressure  steam  system  with  closed  re- 
turns. This  extra  radiation  serves  to  condense  the  steam 
that  may  be  admitted  to  the  normal  radiator  beyond  its  re- 
quired condensing  capacity.  If  too  much  steam  is  admitted 
for  any  given  outside  temperature  it  will  pass  into  the  re- 
turns and  out  into  the  air.  In  this  system,  therefore,  it  is  very 
desirable  that  the  best  of  regulation  be  applied  to  the  draft  dampers 
at  the  boiler  and  also  that  careful  adjustment  be  made  on 
the  valve  inlets  to  the  radiators.  Since  most  vapor  inlet 
valves  are  hand  operated  and  are  subject  to  the  eccentric- 
ities of  the  attendant,  too  much  dependence  should  not  be 


HOT   WATER   AND   STEAM   HEATING 


133 


Fig:.  55. 


Fig:.  56. 


placed  in  this  regulation.  It  will  be  noticed  that  the  end  of 
the  main  is  separately  vented  and  enters  the  dry  return 
through  a  water  seal.  This  serves  to  cut  off  direct  steam 
circulation  into  the  return.  Two  representative  systems  of 
this  class  are  the  Atmospheric  and  the  Mouat-Squlres. 

The  damper  regulator  of  the  Mouat-Squires  system  is 
worthy  of  special  mention.  Fig:.  56,  tank  A  is  filled  with 
water  to  the  overflowing1  point,  the  overflow  connection  be- 
ing opposite  the  fulcrum.  Steam  enters  the  regulator  from 
the  boiler  through  connection  F,  forces  the  water  down  in 
tank  A  and  up  through  the  flexible  hose  B  and  the  hollow 
lever  C  into  tank  D,  causing  tank  D  to  drop  when  a  sufficient 
weight  of  water  to  overcome  the  weight  of  the  counterbal- 
ance E  has  entered  same.  This  causes  the  drafts  to  close. 
When  the  pressure  decreases  in  the  boiler,  the  water  re- 
turns to  tank  A  by  gravity,  causing  the  reverse  operation  of 
the  regulator  and  dampers.  The  setting  of  the  counter- 
weight E  regulates  the  vapor  pressure  at  which  action 
takes  place. 

A  slightly  modified  form  of  Type  1  (Broomell  System 
Fig.  57)  has  a  receiver  at  the  end  of  the  return  main  at  the 
boiler  and  an  air  relief  from  the  top  of  the  receiver  to  the 
atmosphere.  The  air  relief  leads  through  a  condenser  to 
condense  and  return  to  the  boiler  any  steam  leaving  with 
the  air.  The  end  of  the  main  may  be  separately  vented  or 
connected  with  the  air  relief.  Fig.  58  shows  two  sections  of 
the  receiver.  A  copper  float  rides  on  the  water  in  the  re- 


134 


HEATING  AND  VENTILATION 


Fig.  57. 


Fig".  58. 


ceiver  and  is  connected  by  chain  to  the  dampers.  The  level 
of  the  water  in  the  receiver  remains  the  same  as  that  in  the 
boiler  as  long  as  all  the  steam  generated  in  the  boiler  is 
used  in  heating.  When  excess  steam  is  generated  the  pres- 
sure increases,  the  water  level  rises  in  the  receiver  and  the 
float  closes  the  drafts.  If  the  float  rises  high  enough  to  lift 
the  adjusting  rod,  it  unseats  a  safety  valve  and  blows  off 
the  steam.  The  reverse  action  takes  place  when  the  pres- 
sure drops. 


Fig.  59. 


Fig.  60. 


Type  2,  Fig.  59,  has  no  regulation  on  the  radiator  out- 
lets (radiators  not  shown)  but  has  a  condenser  coil  and 
thermostatic  control  on  the  air  relief  which  connects  with 
both  main  and  return.  By  the  use  of  a  check  valve  or  mer- 
cury seal  beyond  the  thermostatic  valve  a  partial  vacuum 
may  be  temporarily  produced  in  the  system.  In  this  type 
the  amount  of  radiation  is  normal  and  the  steam  pressure 
may  rise  above  normal  with  automatic  air  release  without 
waste  of  steam.  The  Moline  System  is  typical  of  this  class. 
Note  the  ejector,  Fig.  60.  This  is  supplied  with  steam  from 
the  end  of  the  supply  main  and  ejects  the  air  and  vapor 


HOT  WATER  AND   STEAM  HEATING 


135 


from  the  end  of  the  return  main  into  the  condenser,  from 
which  the  air  is  released  through  the  air  trap  and  the  con- 
densation is  returned  to  the  boiler. 

Type  3,  Fig.  61,  has  a  normal  amount  of  radiation,  a 
positive  thermostatic  control  on  the  radiator  outlets  and  an 
air  relief  connecting-  with  the  ends  of  the  main  and  return 
either  mechanically  or  thermostatically  controlled.  Three 
representative  systems  of  this  class  are  the  Dunham,  Webster 
and  Illinois.  Attention  is  called  to  the  equalizer  pipe  be- 


Fig.  61. 

tween  the  main  and  return  at  the  boiler,  the  swing  check 
between  the  return  riser  and  the  boiler  and  the  scale  pocket 
on  the  bottom  of  the  return  riser  to  protect  the  check  from 
scale  and  dirt.  Also  notice  the  difference  in  levels  between 
the  normal  water  line  in  the  boiler  and  the  lowest  end  of 
the  return  main.  This  requires  a  water  column  of  at  least 
27  inches  to  provide  sufficient  head  to  overcome  the  inertia 
of  the  check  and  to  account  for  a  small  differential  pressure 


136 


HEATING  AND   VENTILATION 


Fig.  62. 


between  main  and  return.  The  air  relief  in  this  type  as  in 
the  type  preceding  may  be  made  to  close  under  pressure  and 
pressures  above  normal  may  be  used.  Type  3  gives  a  more 
positive  circulation  in  the  mains  and  radiators,  less  danger 

of    short   circuits    and    greater 
pressure  range  than  those  sys- 

, terns   not  equipped   with   ther- 

\V  °  I  mostatic  valves  on  radiator 
outlets.  Steam  pressure  regu- 
lators, similar  in  action  to  Fig. 
62  are  used  for  damper  control. 
Atmospheric  and  vapor  heat- 
ing systems  that  may  at  times 
be  operating  under  pressures 
varying  from  2  to  10  pounds 
gage  are  fitted  with  return 
traitfi  that  close  the  air  re- 
lief when  the  differential  pressure  between  main  and  re- 
turn reaches  a  fixed  amount.  At  the  same  time  live  steam 
is  automatically  admitted  to  the  top  of  the  trap  forcing  the 
collected  return  water  through  the  check  into  the  boiler. 
The  air  vent  remains  closed  and  action  continues  as  an  ordi- 
nary closed  steam  system  until  the  differential  pressure  falls 

to  normal  when  the  action  is 
reversed  and  it  again  becomes 
an  open  relief  atmospheric  sys- 
tem. The  Webster  return  trap 
(Fig.  63)  shows  one  of  the  sim- 
plest forms  of  these  traps. 

84.  Modified  Open  Tank  Hot 
Water  Systems: — A  number  of 
modifications  have  been  adapted 
to  low  pressure  hot  water  heat- 
ing systems  for  the  purpose  of  increasing  the  tempera- 
tures, pressures  and  velocities  of  the  circulating  water  above 
those  obtained  by  the  open  tank  system.  Out  of  a  large 
number  of  systems  four  of  these  will  be  mentioned  as  type 
representatives.  Increasing  temperatures  permits  a  reduc- 
tion in  radiation  so  as  to  compare  with  that  of  steam  sys- 
tems. This  is  desirable  since  large  radiators  are  an  obstruc- 
tion in  any  room.  With  increased  velocities  pipe  and  fitting 
sizes  may  be  reduced.  This  also  is  very  desirable  in  any 


HOT   WATER  AND   STEAM   HEATING 


137 


system  from  the  standpoint  of  adaptability.     In  addition  any 
reduction  of  this  kind  causes  a  reduction  in  first  cost. 

In  the  Honeywell  System  (Fig.  64)  a  purely  American  sys- 
tem,  a   mercury    seal   tube    is   connected    between   the   upper 
point  of  the  main  riser  and  the  expansion  tank.     This  is  de- 
*  signed  to  hold  a  pressure  within  the  system  at 

<  that    point    of   about    10    pounds    gage.      Water 

[%  from  the  system  fills  the  casement  and  presses 

down  upon  the  top  of  the  mercury  in  the  bowl. 
Increasing  the  pressure  in  the  system  lowers 
the  level  of  the  mercury  in  the  bowl  and  forces 
the  mercury  up  the  central  tube  A  until  the 
differential  pressure  is  neutralized  by  the  static 
head  of  the  mercury.  If  the  pressure  becomes 
great  enough  to  drop  the  level  of  the  mercury 
to  the  tube  entrance,  water  and  steam  will 
force  through  the  mercury  to  chamber  D  and 
from  thence  through  the  expansion  tank  to  the 
over-flow.  Any  mercury  forced  out  of  tube  A  by 
the  velocity  of  the  water  and  steam,  strikes 
deflecting  plate  C  and  drops  back  through  an- 
nular opening  B  to  the  mercury  bulb  below. 
As  the  pressure  is  reduced  in  the  system  the 
mercury  drops  in  tube  A  to  the  level  of  that  in 
the  bulb  and  water  from  the  expansion  tank 
passes  down  through  the  mercury  seal  into 
the  heating  system  to  replace  any  that  has 
been  forced  out  of  the  expansion  tank.  This  action  is 
automatic  and  is  controlled  entirely  by  the  pressure  within 
the  system.  The  only  loss,  if  any,  is  that  amount  of  water 
which  goes  out  the  over-flow.  A  similar  arrangement  is 
used  in  the  Cripps  System.  In  this  the  mercury  seal  is  placed 
beyond  the  expansion  tank  and  puts  the  expansion  tank 
under  pressure. 

The  extra  pressure  made  possible  by  the  Honeywell  or 
Cripps  apparatus  makes  it  possible  to  carry  the  circulating 
water  at  temperatures  as  high  as  240°,  which  is  above  that 
of  the  average  low  pressure  steam  system.  With  tempera- 
tures as  high  as  this  there  is  undoubtedly  an  increased  dif- 
ferential temperature  between  flow  and  return  which  would 
tend  to  increase  the  velocity  of  the  water  and  make  it  pos- 
sible to  reduce  pipe  sizes. 


Fig.  64. 


138 


HEATING  AND  VENTILATION 


The  Koerting  System  (Fig-.  65),  invented  by  German  engi- 
neers, is  an  open  tank  system  with  a  series  of  motor  pipes 
leading  from  the  upper  part  of  the  heater  to  a  mixer,  where 
the  steam  which  has  been  formed  in  the  heater  and  motor 
pipes  is  condensed  by  part  of  the  circulating  water  entering 
through  the  by-pass  from  the  return.  The  velocity  of  the 
steam  and  water  through  the  motor  pipes  and  the  partial 
vacuum  caused  by  the  condensation  in  the  mixer  produces  an 
acceleration  up  the  flow  pipe. 


Fig.  65. 


Fig.  66. 


The  Bruckner  System  (Fig.  66),  invented  by  an  Austrian 
engineer,  is  an  open  tank  system  with  two  expansion  tanks. 
Heater  K  delivers  the  hot  water  (above  212°)  up  the  flow 
pipe  to  receiver  R,  where  a  separation  takes  place  between 
the  steam  particles  and  the  water,  thus  causing  an  accelera- 
tion up  the  motor  pipe  to  expansion  tank  A.  The  water  in 
flow  pipe  2  has  a  temperature  slightly  below  that  in  1.  After 
passing  through  the  radiators  the  water  in  3  is  at  a  lower 
temperature  than  that  in  2.  The  steam  particles  which  have 
collected  in  expansion  tank  A  above  the  water  line  are  con- 
densed in  V.  The  acceleration  in  the  system  is  thus  pro- 
duced by  a  combination  of  the  upward  movement  of  the 


HOT  WATER  AND   STEAM  HEATING 


139 


steam  particles  in  motor  pipe  1  and  the  induced  upward  cur« 
rent  in  3  toward  condenser  V.  It  will  be  noticed  by  compar- 
ing with  Fig-.  65  that  the  condensation  in  one  system  takes 
place  before  the  expansion  tank  and  in  the  other  system 
after  it  has  passed  the  expansion  tank.  Each  of  the  systems 
illustrated  may  be  carried  under  pressure  by  applying  a 
safety  valve  as  at  B,  a  mercury  column  as  in  Fig.  64,  or  by 
an  expansion  tank  located  high  enough  to  give  sufficient 
static  head. 

The  Reck  System,  invented  by  a  Danish  engineer,  is  illus- 
trated  by   Figs.    67   and   68.     Water  passes   from   the   heater 


Fig.  67. 


DETAIL    OF    A,  B.ANDC. 

Fig.  68. 


up  the  main  riser  to  condenser  C  and  thence  into  expansion 
tank  A  as  a  supply  to  the  flow  pipes  of  the  system.  Steam 
from  a  separate  boiler  is  admitted  to  mixer  B  above  the  con- 
denser and  enters  the  circulating  water  just  below  the  ex- 
pansion tank.  The  velocity  of  the  steam  and  the  partial 
vacuum  caused  by  the  condensation  induces  a  current  up  the 
flow  pipe  to  the  expansion  tank.  When  the  water  level  in 
the  expansion  tank  reaches  the  top  of  the  overflow  pipe  the 
water  returns  to  the  steam  boiler  through  condenser  C  where 


140 


HEATING  AND   VENTILATION 


it  gives  off  heat  to  the  upper  current  of  the  circulating 
water.  It  will  be  seen  that  the  circulating  water  in  the 
system  and  the  steam  from  the  boiler  unite  from  the  inlet 
at  the  mixer  to  the  expansion  tank.  On  all  other  parts  of 
the  systems  they  are  independent. 

Fig.  69  is  a  modification  of  this  same  principle,  wherein 
air  is  injected  in  the  riser  pipe  at  B  and  causes  acceleration 
by   a   combination    of   the    partial    vacuum    produced    by   the 
_^  steam     condensation     as    just     men- 

__J|  tioned    and    the    upward    current    of 

jj^— ft  the    air    particles    as    in    an    air    lift. 

Steam  enters  through  pipe  J  and 
ejector  //  to  the  mixer  at  B  where  it 
is  condensed.  In  passing  through  H 
air  is  drawn  from  tank  E  and  enters 
the  main  riser  with  the  steam.  The 
upward  movement  of  this  air 
through  the  motor  pipe  to  the  tank 
induces  an  upward  flow  of  the  water 
in  the  main  riser.  By  this  combina- 
tion there  are  formed  three  complete 
circuits,  water,  steam  and  air,  unit- 
ing as  one  circuit  from  the  mixer  B 
to  expansion  tank  E.  The  steam 
furnished  in  principle  3  may  be  sup- 
plied by  a  separate  steam  boiler  or 
by  steam  coils  in  the  fire  box  of  a  hot  water  boiler. 

Acceleration  is  also  produced  by  some  piece  of  mechan- 
ism as  a  pump  or  motor  placed  directly  in  the  circuit.  This 
principle  is  discussed  under  District  Heating  and  will  be 
omitted  here. 

85.  Gas-  and  Electric-Steam  Heating  Systems: — A  gas- 
steam  system  of  heating,  similar  in  many  respects  to  the 
Rector  gas  radiator  system  (Art.  74),  is  frequently  used.  In 
this  case  the  heating  unit  is  a  combination  gas  stove  and 
steam  radiator.  The  gas  supply  (either  natural  or  artificial) 
is  automatically  controlled  by  a  diaphragm  valve  from  the 
pressure  within  the  radiator.  Radiators  without  exhaust 
pipes  may  be  used  with  artificial  gas  for  limited  heating,  but 
they  should  be  supplied  with  exhaust  pipes  in  every  case 
where  natural  gas  is  used  and  where  artificial  gas  is  used  in 
amounts  to  render  the  room  air  impure.  An  electric- steam 


HOT   WATER   AND    STEAM   HEATING 


141 


system  is  sometimes  used  for  the  same  service.  The  radia- 
tors are  made  of  pressed  steel,  electrically  welded  and  sealed. 
The  radiator  contains  a  small  amount  of  distilled  water  (a 
6-section  type  having  about  a  quart  which  never  needs  re- 
placing). The  electric  heating  unit  is  about  the  same  capac- 
ity as  those  used  in  electric  flat  irons.  The  heating  unit, 
partially  "surrounded  by  water  and  under  partial  vacuum, 
heats  readily.  Systems  of  this  type  are  in  use  in  climates 
where  only  moderate  heating  is  necessary. 

8ft.      Piping    Connections: — Many    heating    systems    have 


TEE  BRANCH 


(4)     i 


BRANCHES  IN 
SAME  PLANE 


DOUBLE  ELL 
BRANCH 


( I)   DRAINAG-E  ON 
STRAIGHT  RUN 
REDUCTION  IN  PIPE 


(5) 

Y  BRANCH 


(8) 

BOXING  MAIN 
AROUND   BEAM 


Fig.  70. 


142 


HEATING  AND  VENTILATION 


been  crippled  by  improper  piping  connections.  Figs.  70  and 
71  show  some  of  the  standard  forms.  In  this  connection  a 
few  suggestions  may  be  valuable.  (1)  A  steam  main  may 
branch  right  and  left  through  a  straight  tee  providing  the 
lineal  expansion  of  the  branches  is  provided  for.  (2)  Right 


(9) 

MAIN.  BRANCH 

TO  RISER 
PERPENDICULAR  AND 
PARALLEL  TO  WAI 


(10)  J«J  MAIN  BRANCH 

_      TO  RISER 
DOUBLE  PITCH  ELLS 


03) 


DIRT  POCKET 

i  BOTTOM  OF  RISER 

REMOVABLE  CAP 


f  0.  S.  FITTING 
_J  ON  RISER  TO 
UPPER  RADIATOR 


MAIN  BRANCH 
TO  RISER  45° 
AND  DOUBLE  PITCH  ELL 


n 


(12)  O 


MAIN  RETURN  BRANCH 
DOUBLE  PITCH  ELL 


Fig.  71. 

and  left  branches  through  straight  tees  in  hot  water  sys- 
tems should  never  be  used.  A  double  sweep  ell  should  be 
used  instead,  this  will  divide  the  two  streams  of  water  with- 
out causing  eddy  currents.  (3)  Any  branch  that  is  to  be 
favored  should  be  taken  from  the  top  of  the  main  by  vertical 


HOT   WATER  AND   STEAM  HEATING  143 

or  45°  lines.  No  hot  water  branches  should  ever  be  taken 
off  the  side  of  the  main.  (4)  Offset  branches  provide  ex- 
pansion facilities.  (5)  Hot  water  mains  may  branch  through 
Y  fittings.  This  is  ideal  for  circulation  but  does  not  absorb 
expansion  as  readily  as  90°  turns.  (6,  7)  Steam  mains  which 
change  size  should  be  graded  on  the  bottom  for  satisfactory 
drainage.  This  may  be  done  at  a  corner  by  a  reducing  ell 
pitched  slightly  downward  or  on  a  straight  run  by  an  eccen- 
tric fitting.  (8)  Steam  mains  may  pass  an  obstruction  by 
boxing  around  the  obstruction,  the  drop  providing  drainage 
and  the  rise  the  steam  circuit.  (9)  Mains  are  kept  2l/2  to  3 
feet  from  the  wall,  well  supported  from  the  ceiling  and  free 
to  move  in  any  direction  to  allow  for  expansion.  The  cor- 
ners of  the  main  should  not  be  anchored  by  running  diagon- 
ally to  the  riser.  Branches  should  be  run  perpendicular  to 
and  parallel  with  the  wall.  (10,  11,  12)  Double-pitch  ells 
should  lead  to  risers  in  all  places  where  necessary.  Long 
branches  to  risers  are  to  be  avoided  where  possible.  (13) 
Dirt  pockets  should  be  provided  at  the  bottom  of  return 
risers  where  there  is  danger  of  clogging  valves.  (14,  15, 
16)  Radiation  on  the  upper  floors  will  rob  the  lower  floor 
radiation,  consequently  retarding  influences  such  as  O.  S. 
fittings,  reducers  and  offsets  should  be  put  in  to  give  advan- 
tage to  lower  floors.  (17)  Radiators  should  be  connected 
with  branches  sufficiently  long  to  take  up  expansion.  (18) 
Water  pockets  should  be  avoided  in  horizontal  mains  and 
branches.  All  pipes  should  be  well  pitched  for  drainage.  (19) 
Risers  may  be  run  within  the  wall  or  in  closed  chases  in  the 
face  of  the  wall  for  appearances.  Complete  encasement 
within  the  wall,  however,  should  be  made  only  with  the 
knowledge  and  consent  of  the  owner  since  in  many  cases 
walls  have  been  ruined  by  defective  pipes.  (20)  Branches 
may  also  be  run  within  the  floor  construction,  but  extra  care 
should  be  used  in  the  laying. 


CHAPTER   VII. 


HOT    WATER    AND    STEAM    HEATING 


BOILERS,   RADIATORS,   FITTINGS   AND   APPLIANCES. 

87.  Steam  Boilers  and  Water  Heaters: — Heaters  for 
supplying1  hot  water  and  boilers  for  supplying  steam  to 
heating  systems  may  be  divided  into  three  classes:  round 
vertical,  having  capacities  of  250  to  1500  sq.  ft.;  sectional, 
having  capacities  of  300  to  9000  sq.  ft.;  and  water  tube  or  fire 
tube,  having  capacities  of  10000  to  40000  square  feet  of  direct 
steam  radiation.  Round  and  Sectional  boilers  (Figs.  72  and 
73)  are  made  of  cast  iron,  are  of  the  portable  type  and  need 
no  special  casings  other  than  the  plastic  coverings  to  reduce 
radiation.  Fire  tube  and  water  tube  boilers  (Figs.  74  and 
75)  are  of  wrought  iron  or  steel  and  are  encased  in  brick 
work.  Boilers  of  the  largest  capacities  are  water  tube  type 
and  are  always  used  in  central  station  work.  Heating  boil- 
ers for  residence  work  are  usually  of  the  sectional  type.  These 
boilers  are  very  flexible  and  may  be  increased  in  capacity  by 
adding  sections  to  existing  boilers  to  meet  increased  require- 
ments. In  some  installations  it  is  better  to  install  two 
boilers  of  somewhat  reduced  capacity  (say  %  of  the  calcu- 
lated capacity)  and  either  boiler  will  more  nearly  meet  the 
average  load.  This  is  frequently  done  where  break  downs 
may  cause  serious  inconvenience.  In  general  it  may  be  said 
that  products  of  the  various  manufacturers  show  but  little 
difference  in  design  between  hot  water  heaters  and  steam 
boilers  and  as  a  result  the  two  types  are  usually  referred  to 
as  boilers.  * 

Boiler  capacity  depends  principally  upon  the  amount  and 
arrangement  of  the  grate  and  heating  surfaces.  Grate  sur- 
face is  the  gross  area  of  the  fuel  bed  at  the  top  of  the  grate. 
Heating  surface  refers  to  those  boiler  plates  that  have  the 
fire  or  heated  gases  on  one  side  and  water  on  the  other. 
Heating  surfaces  are  of  two  kinds,  direct  and  indirect  (some- 
times called  prime  and  secondary).  Direct  surfaces  are  those 
so  located  as  to  receive  the  direct  heat  or  radiant  ray  of 


HOT  WATER  AND   STEAM   HEATING  145 


FlQ.     75 


146 


HEATING  AND   VENTILATION 


the  fire.  Indirect  surfaces  are  all  those  not  included  under 
direct,  i.  e.,  those  that  are  in  contact  only  with  the  heated 
gases  of  combustion.  Direct  surfaces  transmit  more  heat 
per  unit  of  time  than  the  same  area  of  indirect  surface  be- 
cause of  the  greater  difference  in  temperature  between  the 
two  sides  of  the  plate.  For  this  reason  boilers  have  as  much 
direct  surface  as  is  possible  to  give  them.  The  average 
amount  of  heat  transmitted  through  boiler  plates  will  vary 
from  1600  to  2500  B.  t.  u.,  for  heating  boilers  and  2000  to 
3000  B.  t.  u.,  for  power  boilers.  The  rate  of  heat  transmission 
for  clean  metal  surfaces  should  be  practically  the  same  for 
either  direct  or  indirect  locations.  See  also  Art.  61  on  fur- 
nace heating  surfaces. 

Proper  combustion  of  the  fuel  and  the  most  efficient 
transmission  of  the  heat  of  the  fire  across  the  plates  to  the 
water  are  of  prime  importance.  It  is  easy  to  see  therefore 


Fig.  76. 

that  the  one  feature  of  boiler  design  under  continual  study 
is  the  construction  of  the  fire  box  or  furnace.  This  is 
especially  true  of  the  boilers  burning  bituminous  or  soft 
coals.  The  average  hand  fired  furnace,  cared  for  by  the 
average  fireman  is  a  nuisance  in  any  business  or  residence 
district  because  of  the  smoke.  In  large  plants  the  mechan- 
ical stoker  which  fires  slowly  and  continuously  at  the  front 
of  the  fire  has  proved  the  best  remedy  but  in  small  plants 
where  hand  firing  is  necessary  and  where  the  fire  is  charged 
three  to  four  times  each  twenty-four  hours  the  problem  is 
more  difficult.  A  number  of  smokeless  furnaces,  represented 
by  Fig.  76,  have  been  developed  along  the  lines  of  the 


HOT  WATER   AND   STEAM   HEATINf! 


147 


Hawley  down  draft  furnace  with  water  tube  grates  above 
the  fire  and  fire  grates  below.  Fuel  is  fed  into  the  space 
above  the  water  tubes  (coking  chamber)  and  there  loses 
the  volatile  matter  and  hydrocarbon  gases.  These  gases 
are  practically  all  consumed  in  passing  over  the  lower  fire 
and  through  the  length  of  the  combustion  chamber.  The 
lower  grate  catches  the  coke  product  from  the  upper  grate 
and  is  occasionally  replenished  by  a  charge  of  fresh  coal 
near  the  front  of  the  fire.  These  furnaces  produce  prac- 
tically smokeless  combustion  and  are  being  increasingly 
used. 

The  latest  design  of  soft  coal  furnace  is  that  shown  in  Fig. 
77.     This  is  of  the  sectional  down-draft,  grateless  type  and 


Fig.  77. 

is  especially  designed  for  bituminous  and  soft  coals,  having 
a  magazine  above  the  fire  which  serves  the  purpose  of  sup- 
ply box  and  coking  chamber.  In  this  arrangement  com- 
bustion takes  place  as  in  the  Hawley  furnace,  the  liberated 
hydrocarbons  being  consumed  while  passing  through  the 
entire  length  of  the  combustion  chamber  to  the  chimney. 


148  HEATING  AND  VENTILATION 

Round  and  sectional  types  of  boilers  have  ratios  of 
grate  surface  to  heating-  surface  varying  between  1  to  15 
and  1  to  25,  and  water  tube  or  fire  tube  boilers  varying  be- 
tween 1  to  40  and  1  to  60.  The  arrangement  of  the  heating 
surface  differs  very  much,  each  manufactured  product  hav- 
ing a  distinctive  design.  According  to  Prof.  Kent  "for  com- 
mercial and  constructive  reasons,  it  is  not  convenient  to 
establish  a  fixed  ratio  of  heating  surface  to  grate  surface 
for  all  sizes  of  boilers.  The  grate  surface  is  limited  by  the 
available  area  in  which  it  may  be  placed,  but  on  a  given 
grate  more  heating  surface  may  be  piled  in  one  form  of 
boiler  than  in  another,  and  in  boilers  of  one  general  form 
one  boiler  may  be  built  higher  than  another,  thus  obtaining 
a  greater  amount  of  heating  surface.  The  rate  of  burning 
coal  and  the  ratio  of  heating  to  grate  surface  both  being 
variable,  the  coal  burning  rate  and  the  ratio  may  be  so  re- 
lated to  each  other  as  to  establish  a  rate  of  evaporation  of 
2  Ibs.  of  water  from  and  at  212°  per  sq.  ft.  of  heating  sur- 
face per  hour." 

Boilers  may  be  selected  by  grate  surface,  heating  surface, 
coal  burned  per  hour,  pounds  of  steam  evaporated  per  hour 
and  heating  capacity  in  square  feet  of  radiation  (including 
mains).  Manufacturers'  catalogs  give  boiler  ratings  in 
terms  of  radiation  supplied,  with  grate  surface,  heating 
surface  and  installation  sizes  for  units  of  different  capac- 
ities. The  best  method  of  selecting  a  heating  boiler  is  to 
estimate  the  required  grate  surface  of  the  boiler  that  will 
theoretically  supply  the  given  radiation  and  check  this 
amount  with  the  catalog  data  (See  Art.  100).  Considerable 
care  must  be  exercised  in  the  selection  of  the  type  of  boiler 
to  fit  any  g-iven  set  of  conditions.  To  illustrate:  the  grate 
and  fire  box  should  be  designed  favorable  to  the  burning  of 
the  kind  of  coal  that  would  be  generally  used;  the  boiler 
selected  should  permit  of  easy  cleaning  especially  if  it  is  a 
soft  coal  burner;  the  arrangement  of  the  heating  surfaces 
should  be  such  that  there  will  not  be  an  excessive  friction 
as  the  g-ases  pass  through  the  boiler;  with  an  inside  chim- 
ney there  is  little  danger  of  lack  of  draft  and  any  form  of 
down  draft  boiler  may  be  used,  while  with  an  outside  chim- 
ney of  ordinary  construction  there  may  be  a  question  as  to 
the  use  of  such  boilers;  also,  the  kind  of  attention  and  the 
frequency  of  firing  must  be  taken  into  account.  For  fur- 
ther study  of  boiler  types  and  operations  see  Marks'  M.  E. 


HOT   WATER  AND   STEAM   HEATING  149 

Handbook,  Kent's  M.  E.  Pocket-Book,  Gebhardt's  Steam 
Power  Plant  Engineering1,  Hirshfield  and  Barnhard's  Ele- 
ments of  Heat  Power  Engineering-,  and  trade  catalogs. 

Combination  heaters  are  frequently  installed  to  supply  both 
warm  air  and  steam  or  warm  air  and  warm  water  to  the 
same  plant.  For  such  systems  a  combination  heater  as 
shown  in  Fig'.  26,  Art.  65,  is  needed.  It  consists  essentially 
of  a  warm  air  furnace  with  a  steam  or  water  radiator  in 
the  upper  part  of  the  fire  pot.  The  radiator  through  the 
connected  piping  supplies  heat  to  those  sections  of  the  build- 
ing where  satisfactory  air  circulation  could  not  be  had.  The 
principal  difficulty  encountered  in  these  combined  systems 
is  in  obtaining  the  proper  proportion  of  the  heating  surface 
of  the  furnace  to  that  of  the  radiator  to  suit  varying  de- 
mands upon  the  system. 

88.  Boiler  Accessories: — Water  heaters  are  equipped 
with  pressure  gages  or  mercury  columns  for  registering  the 
pressures  carried  within  the  system,  thermometers  on  the 
supply  and  return  mains  to  give  the  differential  tempera- 


Fig.  78.  Fig.  79. 

ture  of  the  circulating  water,  and  automatic  draft  apparatus 
controlled  by  thermo-regulation  from  the  temperatures  of 
the  supply  water  or  by  a  thermostat  from  the  temperature 
of  the  room  air.  St-eam  boilers  are  supplied  with  pressure 
gages  as  in  water  heaters,  safety  valves  or  pop  valves  to 
relieve  any  excessive  pressures,  water  glass  and  gage  cocks 
to  register  the  water  levels,  and  automatic  draft  apparatus 
controlled  by  a  diaphragm  valve  from  the  pressure  of  the 
steam  in  the  supply  main,  by  a  float  from  the  water  level  in 
the  return  main  or  by  a  thermostat  from  the  temperature  of 
the  room  air.  Fig.  78  is  a  thermo-regulator  for  water 
systems.  It  operates  from  the  elongation  and  contraction 
of  a  sylphon  bellows  enclosed  within  a  cast  iron  casing. 


150  HEATING  AND   VENTILATION 

The  bellows,  a  brass,  accordion  pleated  cylinder,  is  closed  at 
both  ends  and  contains  a  volatile  fluid  which  vaporizes  at 
low  temperatures  and  causes  varying  pressure  within  the 
bellows.  Water  from  the  boiler  circulates  between  the  bel- 
lows and  the  casement  and  as  the  temperature  of  the  water 
changes  the  state  of  the  volatile  liquid  its  pressure  changes 
and  the  bellows  increases  or  decreases  in  length  and  oper- 
ates the  draft.  A  modification  of  this  type  of  regulator  is 
used  on  steam  system.  In  this  the  regulation  is  by  steam 
pressure  from  the  inside  of  the  sylphon  bellows  (see  Fig.  62). 

Fig.  79  shows  a  diaphragm  regulator  which  is  usually 
attached  to  the  steam  space  of  the  boiler  or  to  the  steam 
main  close  to  the  boiler.  For  details  of  specialties  including 
glass  gages,  gage  cocks,  etc.,  see  American  Radiator  and 
United  States  Radiator  company's  catalogs.  For  care  of 
boilers  and  furnishings  see  Art.  115. 

89.  Radiators,  Classification  as  to  Material: — Radiators 
may  be  classified  according  to  the  materials  used  in  their 
production  as  cast  iron,  pressed  steel  and  pipe  coil.  Wall 
thicknesses  of  cast  radiators  are  %  to  •&  inch.  Pressed 
radiators  are  formed  from  sheet  steel  plates.  Each  section  is 
composed  of  two  pressed  sheets  that  are  welded  together  by 
a  double  seam  around  the  edge  and  riveted  between  the  col- 
umns. The  sections  of  cast  radiators  are  connected  by  mild 
steel  or  malleable  push  or  screw  nipples  which  serve  as  pas- 
sageways between  the  sections  for  the  heating  medium. 
The  malleable  nipple  is  subject  to  occasional  hidden  defects 
from  the  process  of  casting  but  is  not  subject  to  corrosion 
as  is  true  of  the  steel  nipple,  hence  it  is  usually  preferred. 
Pressed  steel  sections  are  welded  together.  Cast  iron  radia- 
tors have  the  disadvantage  of  weight  and  bulk  and  have  a 
comparatively  large  internal  volume,  averaging  a  pint  and 
a  half  per  square  foot  of  surface,  but  they  are  practically 
free  from  corrosion.  Each  radiator  after  being  assembled 
is  tested  to  100  Ibs.  per  sq.  in.  gage  pressure.  Pressed  radia- 
tors have  an  internal  volume  approximating  one  pint  per 
square  foot  of  surface. 

Radiators  composed  of  pipes  in  various  forms  (vertical 
or  horizontal)  are  commonly  referred  to  as  coils.  They  are 
not  much  used  for  direct  or  direct-indirect  work  because  of 
the  unsightliness.  They  are  frequently  used  in  indirect  and 
plenum  systems  and  are  generally  used  in  the  direct  heating 
of  shops,  factories  and  greenhouses.  In  coil  heaters  1-inch 


HOT  WATER  AND   STEAM  HEATING  151 

pipe  is  the  standard  size,  however,  in  some  cases  (green- 
houses) coils  are  used  as  large  as  2  inches  in  diameter. 
Standard  1-inch  pipe  is  rated  at  one  square  foot  of  heating 
surface  per  three  lineal  feet  and  has  about  one  pint  of 
containing  capacity  per  square  foot  of  heating  surface. 

90.  Classification  as  to  Form: — Radiators  may  be  classi- 
fied according  to  form  as  one,  two,  three  and  four  column 
floor  types,  wall  type  and  flue  type.  These  Jerms  refer  only  to 
cast  and  pressed  radiators.  The  column  of  a  radiator  is  one 
of  the  unit  fluid-containing  elements  of  which  a  section  is 
composed.  When  a  section  has  only  one  vertical  unit  it  is 
called  a  single  column  or  one  column  radiator,  when  it  has 
more  than  one  it  is  a  two  column,  three  column  or  four 
column  type.  End  sections  are  called  leg  sections,  inter- 
mediate ones  are  loop  sections.  The  legs  on  all  pressed  steel 
radiators  are  detachable.  A  wall  radiator  is  a  one-column 
type,  so  designed  as  to  be  of  the  least  practicable  thickness. 
It  frequently  presents  the  appearance  of  a  heavy  grating 
and  is  designed  to  have  5,  7  or  9  square  feet  of  surface,  ac- 
cording to  the  size  of  the  section.  One  column  floor  radia- 
tors made  without  feet  are  often  used  as  wall  radiators. 
A  flue  radiator  is  a  very  broad  type  of  the  one  column  radia- 
tor, the  parts  being  so  designed  that  the  air  entering  be- 
tween the  sections  from  below  is  compelled  to  travel  to  the 
top  of  the  sections  before  leaving  the  radiator.  This  type 
is  well  adapted  to  direct-indirect  work. 

There  are  many  special  shapes  of  assembled  radiators 
such  as  stairway  radiators  built  up  of  successive  heights  of 
sections  to  fit  along  the  triangular  shaped  wall  space  under 
stairways,  pantry  radiators  built  up  of  sections  to  form  a  tier 
of  heated  shelves,  dining  room  radiators  with  an  oven-like 
arrangement  built  in  between  sections,  and  window  radiators 
built  with  low  sections  in  the  middle  and  higher  ones  at 
either  end  to  fit  neatly  around  a  low  window.  Fig.  80  shows 
a  number  of  these  common  forms  used  in  practice.  Figs. 
81,  135-137,  show  methods  of  building  up  pipe  coil  heaters. 

01.  Classification  as  to  Heating  Medium: — A  third  classi- 
fication according  to  the  heating  medium  employed,  gives 
rise  to  the  terms  steam  radiator  and  hot  water  radiator.  Cas- 
ually one  would  notice  little  difference  between  the  two,  but 
in  construction  there  is  a  vital  difference.  A  steam  radiator 
has  its  sections  joined  by  nipples  along  the  bottom  only, 
but  a  hot  water  radiator  has  both  top  and  bottom  connec- 


152 


IIKATIXC    AND    VKXT  FLA  TI<>.\ 


Stairway  Type      Dining  Room  Type      Flue  Type      Circular  Type 
CAST   RADIATORS 


Wall  Type 


Two-Column  Three-Column 

Type  Type 


PRESSED   RADIATORS 


Single-Column     Two-Column          Three-Column 
Type  Type  Type 


Four-Column 
Type 


Wall  Type 


Fig-.  80. 


HOT  WATER   AND   STEAM   HEATING 


153 


tions.  This  is  quite  essential  to  the  proper  circulation  of  the 
water.  Steam  type  radiators  are  always  tapped  for  pipe 
connections  at  the  bottom.  Hot  water  radiators  may  have 
the  supply  connections  at  the  top  and  the  return  connections 
at  the  bottom,  or  both  connections  at  the  bottom.  Hot  water 
radiators  can  be  heated  very  successfully  with  steam,  but 
steam  radiators  cannot  be  used  for  hot  water.  Vapor  -sys- 
tems are  supplied  with  two-pipe,  hot  water  type  radiators. 
Radiators  must  have  at  least  two  tappings,  one  below  for 
the  entry  and  exit  of  the  heating-  medium,  and  one  on  the 
end  section  opposite  (near  mid-height  for  steam  and  at  the 

top  for  hot  water)  for  air 
discharge  as  shown  by  Figs. 
46  and  48.  They  may  have 
three  tappings,  a  supply,  a 
return  and  an  air  tapping-  as 
shown  in  Fig's.  47,  49,  50  and 
51  (For  fittings  see  Figs. 
88-92). 

92.  Effect  of  Height  and 
Width  of  Radiator  Upon 
the  Transmission  of  Heat: 
— In  selecting  a  radiator 
height  for  a  given  place  the 
governing  feature  is  usu- 
ally the  floor  space  allowed 
for  the  radiator.  Thus,  if 
a  radiator  26  inches  high 
requires  so  many  sections 
that  it  is  too  long  for  the 
space  allowed,  a  32-inch  or 
a  38-inch  section  may  have 
to  be  taken.  High  radiators  are  less  efficient  than  low  radia- 
tors because  as  the  air  is  heated  in  passing  up  the  outside  of 
the  sections  the  differential  temperature  between  the  inside 
and  the  outside  becomes  less,  and  less  heat  is  transmitted  per 
unit  area.  By  the  same  reasoning,  horizontal  pipes  (coils)  are 
more  efficient  than  any  other  form  of  heating  surface. 
Also,  wide  radiators  are  less  efficient  than  narrow  radiators 
because  of  higher  air  temperatures  between  the  coils. 


Fig.  81. 


154  HEATING  AND  VENTILATION 

Rates  of  heat  transmission  obtained  by  tests  for  cast 
iron  radiators  and  pipe  coils  are:  (Steam  215°,  room  air  70°). 

Cast  Radiators  1-Col.  2-Col.  3-Col.  4-Col. 

20  inches  high              1.93  1.85  1.75  1.64 

23        "  1.89  1.80  1.70  1.59 

26        "  "                   1.86  1.76  1.66  1.56 

32        "  1.79  1.69  1.59  1.49 

38        "  "                   1.74  1.65  1.55  1.45 

45        "  "  1.60  1.50  1.40 

Cast  Wall  Coils 

Heating  surface  5  sq.  ft.,  long-  side  vertical 1.92 

Heating  surface  5  sq.  ft.,  long  side  horizontal 2.11 

Heating  surface  7  sq.  ft.,  long  side  vertical 1.70 

Heating  surface  7  sq.  ft.,  long  side  horizontal 1.92 

Heating  surface  9  sq.  ft.,  long  side  vertical 1.77 

Heating  surface  9  sq.  ft.,  long  side  horizontal 1.98 

Pipe  Coils 

Single  horizontal  pipe  2.65 

Single  vertical  pipe  2.55 

Pipe  coil  4  pipes  high   , 2.48 

Pipe  coil   6  pipes  high   2.30 

Pipe  coil  9   pipes  high  2.12 

93.  Effect  of  Condition  of  Radiator  Surface  on  the 
Transmission  of  Heat: — The  efficiency  of  a  radiator  is  af- 
fected by  the  condition  of  its  outer  surface.  Painting,  bronz- 
ing, shellacing  or  covering  the  radiator  surface  in  any  man- 
ner affects  the  rate  of  transmission  of  heat.  A  series  of 
tests  conducted  by  Prof.  Allen  at  the  University  of  Michigan, 
indicated  that  the  ordinary  bronzes  of  copper,  zinc  or  alum- 
inum caused  a  reduction  in  the  efficiency  below  that  of  the 
ordinary  rough  surface  of  the  radiator  of  20  per  cent.,  while 
white  zinc  paint,  terra  cotta  enamel  and  white  enamel  gave 
the  greatest  efficiency,  being  slightly  above  that  of  the 
original  surface.  Numerous  coats  of  paint,  even  as  high  as 
twelve,  seemed  to  affect  the  efficiency  in  no  appreciable 
manner,  it  being  the  last  or  outer  coat  that  always  deter- 
mined at  what  rate  the  radiator  would  transmit  its  heat. 
Reference. — Trans.  A.  S.  H,  &  V.  E.  The  Effect  of  Painting 
Radiator  Surfaces,  J.  R.  Allen,  Vol.  XV,  p.  229. 


HOT  WATER  AND   STEAM  HEATING 


155 


94.  Effect  of  Housing  on  the  Heat  Transmission  of 
Radiators: — Experiments  were  conducted  by  Prof.  K.  Brab- 
bee  of  the  Royal  Technical  Institute  of  Berlin,  to  determine 
a  relation  between  the  efficiencies  of  exposed  and  enclosed 
radiators.  The  results  of  these  tests  were  reported  in  the 
Heating  and  Ventilating  Magazine,  May,  1914,  and  the  fol- 
lowing is  a  brief  summary.  No  records  were  kept  of  vol- 
umes and  temperatures  of  the  air,  these  differing  so  greatly 
that  the  observations  were  of  little  value.  The  radiators 
used  were  two  and  three  column,  plain  surface,  ten  sections, 
three  inch  centers.  The  two  column  radiators  were  8.5 
inches  wide  and  the  three  column  radiators  were  9  inches 
wide. 

Tests  were  first  run  with  the  radiators  set  in  the  ordi- 
nary way  (2.5  inches  from  the  wall,  not  enclosed  and  in 


il 


E  F  G 

Fig.  82. 

what  is  ordinarily  called  still  air)  giving  results  for  K  as 
follows:  49  in.  2  col.  =  1.62;  24  in.  2  col.  =  1.74;  50  in.  3 
col.  =  1.38;  26  in.  3  col.  =  1.5.  These  values  were  then  used 
as  a  basis  of  comparison  for  showing  increased  or  reduced 
efficiencies  of  various  housings.  At  the  conclusion  of  the 
first  series,  tests  were  conducted  upon  the  same  radiators 
housed  as  shown  in  Fig.  82. 


156  HEATING  AND  VENTILATION 

RESULTS  FOUND. 

A.  The  best  spacing  was  found  to  be  r  =  f  —   2.5  inches, 
although  K  was  about  8  per  cent,  less  than  in  normal  setting 
when    thus    enclosed.      O    should    be    at    least    the    width    and 
length  of  the  radiator.     When  O  was  less   than   this  amount 
K  rapidly  decreased.     For  open  inlets  f  =:  length  of  radiator 
and  d  min.   =   4  inches.     In  such  cases  K  was  reduced  15  per 
cent.     With  inlet  screened  A'  was  much  less. 

B.  With   r    =    f   —    2.5*inches,    the   housing   without   top 
increased  K  as  much  as  12  per  cent,  because  of  the  increased 
velocity  of  the  air  over  the  radiator  due  to  the  chimney  action. 
The   best  results  were   obtained  when   the   area   of  the   inlet 
in   square    inches   was  approximately   ten   times   the   heating 
surface  of  the  radiator  in  square  feet.     K  increased  by  mak- 
ing enclosure  higher  than  radiator. 

C.  Narrow   shelves   placed    3    inches   or   more   above    the 
radiators  had  little  effect.     Where  a  was  such  as  to  be  flush 
with   the   front   of   the   radiator   and   t    =    3    inches   K  fell   off 
about   5   per  cent.     On   low   radiators   the  loss  was  about   10 
per  cent.     In  either  high  or  low  radiators  where  t  —   4  to  5 
inches,  K  was  about  normal.     Curved  deflectors  under  shelves 
showed  little  or  no  gain  in  efficiency  over  the  square  corner. 

D.  Make  r  =   2.5  inches  and  t  —   3  to  6  inches.     Where 
t  =  3  inches  K  was  reduced  8  per  cent.     Where  t  =.   6  inches, 
K  was  approximately  normal.     Side  spacing  had  little  or  no 
effect. 

E.  A  very  inefficient  form  of  housing  even  with  d  and 
o  open  slots.     Under  the  very  best  conditions  K  was  reduced 
25  to  35  per  cent. 

F.  With  r  =  f  =  t  =  2.5  inches,  K  was  reduced  about  20 
per  cent. 

G.  A  very  inefficient  form   of  housing.     K  was  reduced 
30  to  40  per  cent. 

Tests  of  hot  water  radiators  under  the  same  conditions 
of  housing  verified  the  values  found  for  steam.  A  convenient 
way  to  apply  the  above  is  to  figure  the  square  feet  of  radiator 
surface  for  normal  setting  and  then  multiply  this  amount  by 
the  following  approximate  values:  A,  1.10;  B,  1.00;  C,  1.07; 
D,  1.10;  E,  1.30;  F,  1.20;  G,  1.40. 

In  places  where  direct-indirect  radiation  is  desired  and 
no  provision  has  been  made  for  it  in  the  building  plan.  Fig. 
83  is  suggested  as  a  good  substitute.  The  housing  around 


HOT   WATER  AND   STEAM   HEATING 


157 


the  radiator  accelerates  the  draft,  and  the  damper  arrange- 
ments g-ive  opportunity  for  all  outside  air,  mixed  outside  and 
inside  or  all  inside  air  at  the  discretion  of  the  occupants. 

95.  Amount  of  surface  in  Radiat- 
ors:— Table   XIII   gives  according   to 
the    columns   and   heights,    the    num- 
ber of  square   feet  of  radiation   sur- 
face per  section  in  cast  and  pressed 
radiators.      This    table    presents    ap- 
proximate   values    in    very    compact 
form    from    extended    tables    in    the 
manufacturers'  catalogs.  An  approx- 
imate  rule   supplementing   this  table 
and  giving,  to  a  very  fair  degree  of 
accuracy,  the  square  feet  of  surface 
in   any   standard   radiator   section,   is 
as   follows:    multiply   the   height   of   the 
sections  in   inches  l>y  the  number  of  col- 
umns and  divide  by  the  constant  20;  the 
result  is  the  square  feet  of  radiating  sur- 
face   per    section.       The    rule    applies 
with   least    accuracy   to    one   column 
radiators. 

96.  Pipe     Fittings: — Common     and 
special. — Pipes  of  standard  diameters 
and  random   lengths  are  made  from 


Fig.  83. 


both  wrought  iron  and  steel.  These  pipes  are  cut,  threaded 
with  standard  threads  and  connected  with  standard  malleable 
or  cast  iron  fittings  to  form  any  desired  combination.  Wrought 
iron  pipe  is  considered  by  some  to  be  more  durable  than 
steel  pipe  for  general  service  but  because  of  less  first  cost 
steel  is  more  frequently  employed.  For  exact  diameters, 
surfaces,  etc.,  see  Table  29,  Appendix. 

Lengths  of  pipe  are  connected  in  straight  runs  by  unions 
and  couplings.  Unions  are  threaded  right-hand,  and  right- 
and-left.  As  distinguished  from  the  right  union  the  right- 
and-left  has  one  end  tapped  right  hand  and  the  other 
left  hand  and  connects  between  sections  of  a  straight 
run  already  laid.  Flanged  couplings  (usually  packed 
between  the  flanges)  are  generally  employed  in  con- 
necting large  sized  pipes,  and  in  addition  are  used  on 
any  sized  pipe  in  places  where  sections  may  need  fre- 


158 


HEATING  AND  VENTILATION 


TABLE  XIII. 


Dimensions  and  heating-  surfaces  of  radiators,  per  section. 


Type  of 
radiator 

Max.  spread  of 
legs  in  inches 

Ave.  length  per 
section  in  inches 

Square  feet  of  surface  for  over-  all  heights 

45"    38"    32"    26"    23"    22"    20"   18"   17"   16"   14" 

1  Col.  C   I 

5y2 
sy2 

10 

11% 

12% 

8% 
5% 
8% 
12 

2V2 
2% 

2% 

3 

3 
3 

2 

2 
2 

3 
4 

5 
8 

2% 
3% 
4% 
6% 

2 

2% 
3% 
5 

1% 
2% 
3% 
4% 

1% 
2 
2% 
3% 
6 
3V, 

1% 
1% 
2% 
3 
5V3 

2  Col.  C.  I. 

5 

6 
10 

2^4 

4 

—  - 

1% 

.... 

3  Col    C    I 

4  Col.  C.  O  
Flue  wide  

4% 

4% 

4 

Flue  narrow  
1  Col.  press  
3  Col.  press  
4  Col.  press  

6 

7 
3 
5 

5% 
2V2 
4% 

4% 
2 
3% 
4% 

.... 

1% 
3 

1% 

914 

.... 

.... 

1 
1.5 

2% 

.... 

3% 

.... 

3 

.... 

.... 

Wall  rad.  _              A. 

R.  f  13%"x29y8"]    9     13*4"x22"    ]    7 
[  sq.                        [  sq. 
S.   I  14y8"x2!Hi"J  ft.     14H"x22%"J  ft. 

13%"xl6%"l    5 
[•sq. 
14y8"xl6%"|  ft. 

C.  I. 

Thick.  3"                   U. 

quent  removal  for  repairs  or  inspection.  Elbows  (usually 
called  ells)  change  the  direction  of  any  run  through  90°. 
See  double  pitch  ells,  Art  86.  Tees  are  used  where  branches 
leave  a  straight  run  at  90°.  They  are  sometimes  made  with 
a  45°  instead  of  a  90°  branch  and  are  called  laterals  or  Y 
fittings.  Couplings,  elbows,  tees  and  laterals  are  made  with 
varying  inlet  sizes.  These  are  called  reducing  couplings,  re- 
ducing ells,  reducing  tees,  etc.,  and  are  specified  as  follows: 
state  the  sizes  of  the  straight  run,  large  and  small,  and 
second  state  the  size  of  the  branch.  For  illustration,  a 
2"xl%"xl"  reducing-  tee  will  change  the  size  of  the  straight 
run  from  2"  to  iy2"  and  give  a  branch  of  1".  Where  branches 
are  made  for  water  heating-  they  should  be  so  formed  as  to 
give  a  free  and  easy  movement  to  the  water.  In  such  cases 


HOT   WATER  AND   STEAM  HEATING 


159 


it  is  desirable  to  use  pipe  bends  having-  a  radius  of  three  to 
five  pipe  diameters,  instead  of  the  common  elbow.  In  all 
cases  pipe  ends  should  be  carefully  reamed  before  assem- 
bling- to  remove  the  burr  left  by  the  cutter.  This  is  most 
important  in  water  heating-  as  the  burr  on  small  pipes  is 
sometimes  heavy  enough  to  reduce  the  area  of  the  pipe  by 
one-half,  thus  creating  serious  eddy  currents  and  increasing 
the  friction. 


Fig.  84. 

Eccentric  reducing  fittings  (Fig.  84)  are  often  of  value  in 
avoiding  water  pockets  in  steam  lines.  These  should  always 
be  used  on  horizontal  steam  mains  (Fig.  70)  when  reduc- 
tions are  made  from  one  size  to  another.  Bushings  should  not 
be  used  as  reducing  fittings  for  water  lines  because  of  the 
restriction  to  flow  due  to  the  square  end  of  the  bushing. 

Valves  are  of  two  general  types,  globe  and  gate.  Globe 
valves  are  installed  on  steam  lines  but  they  should  not  be 
used  on  horizontal  steam  mains  where  the  seat  will  cause  a 
water  pocket  and  hinder  drainage.  Gate  valves  offer  an  un- 
obstructed passage  for  both 
steam  and  water.  They  are 
recommended  on  all  water 
lines  and  are  being  increas- 
ingly used  on  steam  lines. 
Globe  valves,  however,  are 
less  expensive  and  are  more 
easily  repaired.  The  best 
type  of  globe  valve  has  a 
renewable  composition  seat. 
Fig.  85  shows  sections  of 
each  type 

Radiator  inlet  valves  are  usually  angle  type.  Those  used 
on  the  ordinary  low  pressure  steam  systems  are  packed  with 
soft  packing  and  those  used  on  systems  which  are  occasion- 


160 


HEATING  AND   VENTILATION 


ally  under  partial  vacuum  are  necessarily  of  the  imc-klcxx  type. 
Those  used  on  atmospheric  and  vacuum  systems  generally 
have  graduated  control.  Fig.  86  shows  several  models  of 
these  valves.  Water  radiator  valves  are  of  the  quick  opening 
or  butterfly  type,  opening  and  closing  with  a  quarter  turn  of 
the  handle  and  having  a  small  hole  through  the  valve  to 
permit  just  enough  leakage  when  closed  to  keep  the  radia- 
tor from  freezing.  For  radiator  return  valves  to  be  used  on 
mechanical  vacuum  systems,  See  Chapter  IX. 


Fig.  86. 


HOT   WATER   AXD   STEAM   HE  AT  I  X(  I 


161 


Check  valves  are  of  two  kinds,  swing  and  lift.  They  are  not 
needed  on  the  ordinary  low  pressure  gravity  water  or  steam 
systems,  but  where  used  swing  checks  should  be  specified 
rather  than  lift  checks,  for  the  former  operate  at  less  differ- 
ential pressure  and  offer  much  less  resistance  to  the  passage 
of  water  and  steam.  Fig-.  87  sho.ws  a  section  of  each. 


Fig-.  87. 

Air  valves  serve  a  most  important  function  in  heating 
systems.  Air  is  constantly  accumulating  in  the  radiator 
and  its  frequent  or  automatic  removal  becomes  necessary 
if  all  the  radiating  surfaces  are  to  remain  effective.  For 
this  purpose  small  hand  operated  valves  or  compression 
cocks,  Fig.  88,  are  inserted  near  the  top  of  the  end  section 
in  all  hot  water  radiators,  and  automatic  valves  are  inserted 
at  one-half  to  two-thirds  the  height  of  the  last  section  on 


Fig.  88. 

steam    radiators.      Air   valves   are    not   essential   to   two-pipe 
steam    systems    and    are    sometimes   omitted.      They    are    not 
needed   on   vapor  systems  and  are  always  omitted.      Fig.   89 
shows    a    common    type    of   automatic 
air    valve    using    the    principle    of    the 
expansion  stem.     As  long  as  air  is  in 
contact  with  the  stem  it  remains  con- 
tracted and   the   needle  valve   is  open 
for   air    release.      When    steam    enters 
Fig*.  89.  the   valve   it   surrounds   the   stem   and 

expands  it  sufficiently  to  close  the  needle  valve  and 
prevent  steam  loss.  Fig.  90  operates  on  the  principle 
of  the  evaporation  of  a  volatile  liquid  in  a  closed 
container.  The  composition  of  this  liquid  is  such  that 


162 


HEATING  AND   VENTILATION 


it  evaporates  at  the  steam  temperature  and  causes  a 
deflection  of  the  base'  of  the  container  sufficiently  to  move 
the  valve  pin  and  close  the  valve.  Air  temperatures  being 
less  than  steam  temperatures,  the  reverse  action  takes  place 
when  air  collects  around  the  stem  and  the  valve  opens  for 
air  release.  Water  jetting-,  which  is  frequently  found  with 
air  valves,  is  eliminated  by  the  floatation  of  the  container 
which  is  free  to  lift  and  ride  the  water  that  collects  in  the 
float  chamber.  A  modification  of  this  valve  (Fig.  91)  has, 
in  addition  to  the  thermal  features  just  mentioned,  an  at- 
mospheric air  pressure  feature  which  permits  its  use  on 
vacuum  systems.  As  the  pressure  is  reduced  in  the  radia- 
tor, atmospheric  air  presses  upward  against  diaphragm  1 
and  forces  the  pin  valve  against  its  seat.  It  will  be  seen 
that  when  the  pressure  within  the  radiator  is  less  than 
atmospheric  \he  differential  pressure  closes  the  valve  and 
keeps  air  out.  When  the  pressure  within  the  radiator  is 


Fig.  90.  Fig.  91. 

slightly  above  atmospheric  the  valve  stands  open  except  at 
the  times  when  all  the  air  is  exhausted  and  the  steam  holds 
the  valve  closed  through  the  expansion  member.  By  the 
combined  action  of  both  expansion  members  air  may  be  re- 
leased continuously  but  it  can  not  reenter.  Valves  operat- 
ing on  either  the  thermal  or  differential  pressure  principle 


HOT   WATER   AND   STEAM   HEATING 


163 


or  both  may  be  had  for  quick  venting-  on  mains,  coils  and 
other  parts  of  a  heating-  system.  Figs.  92  and  93  operate  on 
the  principle  of  the  difference  of  expansion  between  two  dis- 
similar metals.  In  the  first  one  the  expansion  member  is 
made  of  two  strips  of  dissimilar  metals  brazed  together  in 
the  form  of  a  loop.  These  metals  expand  at  different  rates 
under  changes  of  heat  and  cause  endwise  movement  of  the 


Fig.  92. 


Fig.  93. 


valve  rod,  thus  opening  or  closing  the  valve.  The  hollow 
float  serves  the  purpose  of  catching  any  sudden  surge  of 
water  and  avoids  flooding.  The  second  one  employs  a  long 
central  tube  which  carries  at  the  top,  the  valve  seat  of  the 
needle  valve.  The  needle  itself  is  carried  by  the  two  side 
rods.  As  long  as  the  air  flows  up  through  the  central  pipe, 
the  needle  valve  will  remain  open,  but  when  steam  enters 
the  tube  it  expands  and  carries  the  valve  seat  upward 
against  the  needle,  thus  closing  the  valve.  The  size  and 
strength  of  parts  make  this  form  a  very  reliable  one.  For  air 
line  valves  to  be  used  on  mechanical  air  line  systems,  see  Chapter  IX. 
97.  Expansion  Tank: — The  expansion  tank  is  a  neces- 
sity in  all  atmospheric  hot  water  systems.  Its  function  is 
to  serve  as  a  supply  tank  for  the  system  and  also  as  a  take- 
up  for  the  excess  volume  due  to  the  heating  of  the  water. 
Fig.  94  shows  a  typical  cylindrical  galvanized  tank  supplied 
in  capacities  of  8,  10,  15,  20,  26,  32,  42,  66,  82  and  100  gallons; 
the  average  size,  16  in.  diam.  x  30  in.  high  is  rated  for 
approximately  1000  square  feet  of  radiation  including  mains. 


164 


HEATING  AND  VENTILATION 


Fig.  95  is  an  automatic,  self-filling,  copper  lined  tank  ap- 
proximately 20  in.  x  9  in.  x  10  in.  and  is  supplied  for  sys- 
tems up  to  2000  square  feet  capacity.  The  galvanized  tank 
is  tapped  1-inch  for  the  overflow  and  expansion  pipes,  and 
the  automatic  tank  is  tapped  %-inch  supply,  li/i-inch  ex- 
pansion and  1  %-inch  overflow.  The  expansion  tank  is  often 

TO 

VENT1LATIN3 
FLUE 


TO  NEAREST  RE 


WATER 

LEVEL 


TO  NEAREST  FLOW 

Fig.  94  Fig.  95. 

located  in  the  bath  room  or  a  closet  near  the  bath  room  and 
its  overflow  connected  to  the  proper  drainage.  It  should 
be  set  at  least  two  feet  above  the  highest  radiator.  The 
connection  between  this  tank  and  the  heating  system  is 
often  by  a  branch  from  the  nearest  radiator  riser.  The  best 
connection  is  by  an  independent  riser  from  the  basement 
return  main.  The  capacity  of  the  tank  for  any  system  up 
to  1500  square  feet  may  be  obtained  by  the  approximate 
rule:  divide  the  total  radiation  l>y  40  to  obtain  the  capacity  of 
the  tank  in  gallons. 

98.  Fire  Coils  or  Water  Backs  for  Hot  Water  Supply: — 
Pipe  coils  or  cast  iron  water  chambers  (water  backs)  may  be 
installed  in  the  combustion  chamber  of  any  furnace,  hot 
water  or  steam  plant  for  heating  the  domestic  hot  water 
supply.  Care  must  be  exercised  in  installing  these  fixtures 
to  see  that  there  is  an  up-flow  for  the  water  from  the  point 
of  entering  to  the  point  of  leaving  the  fire  box.  Soft  water 
should  ~be  used  in  these  water  systems  wherever  possible  because  of 
the  lime  and  other  deposits  thrown  off  from  the  hard  water.  If  it 
becomes  necessary  to  circulate  hard  water  the  coils  should 
be  examined  at  least  once  each  year  to  see  that  they  are  not 
filled  with  lime.  Lime  deposits  cut  down  the  heat  transmis- 
sion, cause  the  pipes  to  burn  and  endanger  the  plant  in 
making  it  more  liable  to  explosion.  In  many  plants  the 
heating  surface  on  these  coils  is  excessive.  On  cold  days 
under  heavy  fire  the  water  in  the  tank  is  maintained  at  the 


HOT  WATER  AND   STEAM   HEATING  165 

boiling  point  when  lower  temperatures  would  be  more  satis- 
factory. This  condition  may  be  corrected  by  attaching-  water 
connections  to  the  circulating  pipes  outside  the  fire  box  and 
running  these  leads  to  a  hot  water  radiator  where  heat  is 
most  needed.  Each  lead  to  the  radiator  and  the  flow  pipe  to 
the  hot  water  tank  should  be  valved  with  gate  valves  so  as 
to  regulate  the  circulation  in  each  line. 

99.  Corrosion  of  Pipes: — Much  has  been  said  and  writ- 
ten about  the  internal  wastage  or  wearing  away  of  steel 
and  wrought  iron  pipes  conveying  hot  water,  but  owing  to 
the  fact  that  such  a  long  time  is  necessary  for  a  compara- 
tive test  and  surrounding  conditions  are  so  changeable,  no 
authoritative  data  have  yet  been  found  to  prove  conclu- 
sively to  pipe  users  that  either  of  the  two  (steel  or  iron)  is 
longer  lived  than  the  other.  Most  of  the  pipe  now  used  in 
the  country  is  of  mild  steel,  probably  because  of  the  fact 
that  this  pipe  can  be  manufactured  and  marketed  at  a  lower 
price.  Nevertheless  if  it  may  be  shown  by  any  conclusive 
proof  that  wrought  iron  pipe  is  more  durable  the  price 
would  be  a  secondary  feature  in  the  purchase.  One  of  the 
most  convincing  papers  on  this  subject  yet  presented  to  the 
engineering  profession  is  found  in  the  Trans.  A.  8.  H.  &  V.  E., 
Vol.  24,  p.  217,  by  F.  N.  Spellor  and  R.  G.  Knowland.  A  copy 
of  the  paper  is  also  found  in  Technical  Paper  236,  Depart- 
ment of  the  Interior,  Bureau  of  Mines. 


CHAPTER  VIII. 


HOT  WATER  AND   STEAM  HEATIXG. 


PRINCIPLES  OF  THE  DESIGN,  WITH  APPLICATION. 

100.  Selecting  Boilers  for  Capacity: — To  determine  the 
necessary  boiler  capacity  for  a  given  installation,  find  the 
theoretical  grate  surface  to  supply  the  calculated  heat  loss 
plus  20  to  30  per  cent,  to  cover  that  lost  from  the  mains  and 
risers,  and  select  a  boiler  having  at  least  this  amount  of 
grate  from  the  catalog  data  representing  the  type  of  boiler 
desired.  Current  practice  adds  25  to  50  per  cent,  to  the 
theoretical  grate  as  a  safety  margin.  Rule. — To  find  the  the- 
oretical grate  surface  in  square  feet,  divide  the  total  B.  t.  u.  required 
per  hour  for  maximum  heating  service  l)y  the  product  of  the  pounds 
of  coal  estimated  per  square  foot  of  grate  surface  per  hour  (rate  of 
combustion),  the  efficiency  of  the  furnace  and  the  heat  value  of  the 
fuel  in  B.  t.  u.  per  pound.  (See  Equation  46). 

The  following  rates  of  combustion  may  be  used  for  in- 
ternally fired  heating  boilers: 


Sq.   ft.   of  grate    _  _      

4-6 

6-10 

10-18 

18-30 

Lbs.  coal  per  sq.  ft.  grate  per  hour  

5 

6 

8 

10 

Boilers  with  constant  attendance,  such  as  power  boilers, 
may  have  a  higher  rate  of  combustion. 

Catalog  ratings  are  usually  obtained  from  test  data 
taken  when  the  boilers  are  burning  anthracite  coal.  Where 
boilers  are  to  be  used  with  soft  coals  the  50  per  cent,  addi- 
tional capacity  mentioned  above  had  best  be  taken  because 
of  the  larger  volume  needed  per  pound  of  coal  and  because 
of  the  sooty  nature  of  the  coals. 

APPLICATION. — Assume  a  total  building  heat  loss  (includ- 
ing mains  and  risers)  of  150000  B.  t.  u.  per  hour;  soft  coal 
13000  B.  t.  u.  per  lb.;  5  pounds  coal  per  sq.  ft.  of  grate  per 
hour;  and  boiler  efficiency  60  per  cent.;  then  from  Equation 


HOT  WATER   AND   STEAM   HEATING  167 

46,  G.  A.  =  550  sq.  in.  Add  50  per  cent.  =  825  sq.  in.  =  5.7 
sq.  ft.  From  the  Ideal  Fitter  this  gives  an  S-25-5.  Sectional 
boiler  with  a  hard  coal  rating-  of  1100  sq.  ft.  of  heating  sur- 
face. 

101.  Calculation  of  Radiator  Surface — Direct  Radiation: 
— In  designing  a  hot  water  or  steam  system,  the  first  impor- 
tant item  to  be  determined  is  the  square  feet  of  radiation  to 
be  installed  in  each  room.  Nearly  all  other  items,  such  as 
pipe  sizes,  grate  area,  boiler  size,  etc.,  are  estimated  with 
relation  to  the  radiation  supplied.  The  correct  determina- 
tion then,  of  the  square  feet  of  radiation  in  these  systems 
is  all  important.  The  general  equation  used  to  obtain  the 
square  feet  of  radiation  for  any  room  is: 

total  B.  t.  u.  lost  from  the  room  per  hour 


R  = 


K  (av.  temp.  diff.  between  inside  and  outside  of  rad.) 


Rule. — To  find  the  square  feet  of  radiation  for  any  room  divide 
the  calculated  heat  loss  in  B.  t.  u.  per  hour  "by  the  quantity  K  times 
the  difference  in  average  temperatures  between  the  inside  and  outside 
of  the  radiator. 

Expressed  in  symbols 

//  (orff') 
/?„,  -  (49) 


/  ta  +  /„  /  +  /„  \ 

V        2~          ~~2        ) 


Rs  =  (50) 


Where  Rw  and  R*  =  sq.  ft.  radiation  required  for  water 
and  steam  heating,  ta  and  tb  —  water  temperatures  entering 
and  leaving  radiators,  t  and  t,,  =  temperatures  of  air  passing 
over  radiator  and  ta  —  temperature  of  the  steam.  In  ordi- 
nary direct  radiation  calculations  the  term  [(*  +  to)  -=-  2]  is 
usually  taken  70. 

In  Art.  92,  the  rate  of  transmission  K,  (Amount  of  heat 
transmitted  through  one  square  foot  of  surface  per  hour  per 
degree  difference  in  temperature  between  the  inside  and  the 
outside  of  the  radiator)  obtained  from  tests,  varies  inversely 
with  both  the  height  and  the  width  of  the  radiator,  being  as 
high  as  1.93  for  low  1-column  and  as  low  as  1.40  for  high 


168  HEATING  AND  VENTILATION 

4-column  radiators.  For  extreme  accuracy  these  values  may 
be  used.  For  ordinary  service,  however,  they  may  be  sum- 
marized with  fair  accuracy  into: 

low  radiators — 16  to  23  inches — 1.8 
medium  "  — 23  to  32  "  — 1.7 
high  "  —32  to  45  "  —1.6 

All  applications  in  this  book  icill  be  taken  1.7. 

With  hot  water  as  the  heating  medium  the  temperatures 
within  the  radiator  for  the  open  tank  system  are  about  as 
follows:  entering  the  radiator  180°;  leaving  the  radiator 
160°;  average  temperature  on  the  water  side  170°.  To  find 
the  amount  of  hot  water  radiation  for  any  other  average 
temperature  of  the  water,  substitute  the  desired  average 
temperature  in  the  place  of  170.  The  maximum  drop  in  tem- 
perature as  the  water  passes  through  the  heater  will  seldom 
be  more  than  20  degrees  even  under  severe  conditions.  The 
temperature  of  the  entering  water  may  be  assumed  as  high  as 
212°  if  it  is  considered  necessary  in  which  case  each  square 
foot  of  surface  becomes  more  efficient  and  the  total  radia- 
tion in  the  room  may  be  reduced.  Since  radiators  become 
less  efficient  from  continued  use,  it  is  best  to  design  a  sys- 
tem with  lower  temperatures  as  stated  and  under  stress  of 
conditions  the  capacity  may  be  increased  by  raising  the 
flow  temperature  to  the  boiling  point.  With  a  room  tem- 
perature of  70°,  a  26-inch  2-col.  or  3-col.  hot  water  radiator 
will  give  off  1.7  X  (170-70)  =  170  B.  t.  u.  per  square  foot 
per  hour  and  the  amount  of  radiation  is: 

For  hot  water,  open  tank  direct  radiation  as  usually  applied 

g  H 

/?,<•   =  -      =  =   .006/7  (51) 

1.7  (170  —  70)  170 

For  the  Honeywell  system  and  others  maintaining  pressures 
above  atmospheric,  use  higher  water  temperatures  in  the 
general  equation.  For  example,  suppose  these  temperatures 
are  entering  at  220°  and  leaving  200°,  we  have 

H  H 

Rw   =  —  =   .0042/7          (52) 

220  +  200  \         238 
70    I 


A  steam  system  may  be  installed   to  work  at  any  pres- 
sure from  a  partial  vacuum  of,  3ay  10  pounds  absolute,  to  as 


HOT  WATER  AND   STEAM   HEATING  169 

high  a  pressure  as  75  pounds  absolute.  To  calculate  the 
proper  radiation  for  any  of  these  conditions  use  Equation  50 
and  substitute  the  proper  steam  temperature. 

The  temperature  within  a  steam  radiator  carrying  steam 
at  pressures  varying  between  0  and  3  pounds  gage  may  be 
taken  220°;  then  the  total  transmission  for  this  radiator  will 
be  1.7  X  (220  —  70)  =  255  B.  t.  u.  per  square  foot  per  hour, 
and  the  amount  of  radiation 

For  Steam,  gravity  direct  radiation  as  usually  applied  is 

H  H  H 

If.,  = = ,  safe  value  =  —    -  —  .004  H     (53) 

1.7  (220  —  70)          255  250 

It  will  be  seen  from  Equations  51  and  53  that  Rw  =  1.5  Rs. 
This  ratio  is  frequently  used  1.6.  (See  also  Art.  137  for 
logarithmic  equation). 

For  atmospheric  and  vapor  systems  with  individual  traps  on 
the  return  end  of  each  radiator 

H  H  H 

Rx  =  -          —  =  ,  safe  value  =  —  —  =  .00417  //  (54) 

1.7  (212  —  70)     241  240 

For  atmospheric  and  vapor  systems  w-ith  open  return  and  20 
per  cent,  excess  radiation  for  cooling  surface 

}{  X  1.2  H 

Ry  =  = =   .005/f  (55) 

1.7  (212  —  70)  200 

Note. — Equations  51  to  55  will  meet  average  conditions. 
If  for  high  radiators,  low  radiators,  wall  or  pipe  coils  it  is 
considered  necessary  to  be  more  specific,  use  the  values  K 
given  in  Art.  92. 

APPLICATION. — Referring  to  the  standard  room  with  H  = 
15267,  Art.  39,  the  equations  quoted  above  give: 

(51)  hot  water,  open  tank  91  sq.  ft. 

(52)  hot  water,  closed  tank  64  sq.  ft. 

(53)  Steam,  0  to  3  Ibs.  61  sq.  ft. 

(54)  Steam,  vapor,  closed  returns  64  sq.  ft. 

(55)  Steam,  vapor,  open  returns  76  sq.  ft. 
Assuming  a  26-inch  3-col.  type  cast  radiator,  we  have  as 

follows: 

for    (51),   24   sections,  radiator  60  inches  long. 

for   (52),  (53),  (54),  17  sections,  radiator  42.5  inches  long. 

for    (55),  21  sections,  radiator  52.5  inches  long. 

Many  empirical  equations  and  rules  have  been  devised 
(based  somewhat  upon  the  rational  Equations  49-55)  in  an 
attempt  to  simplify  calculation,  but  their  applications  are 


170  HEATING  AND  VENTILATION 

untrustworthy  unless  used  with  that  discretion  which  comes 
with  years  of  practical  experience.  The  reason  why  such 
empirical  rules  often  give  erroneous  results  is  because  of 
the  fact  that  nothing-  is  said  concerning-  exposure  and  equiv- 
alent wall,  such  as  floors  and  ceilings.'  Some  of  these  equa- 
tions and  their  applications  to  the  "Study"  Art.  62,  where 
G  =  48,  W  —  192  and  C  =  1900  are: 

G        W        C 

(a)  Rw  = 1 1 '=24  +  19.2  +  31.6  =   74.8  sq.  ft. 

2  10        60 

W  C 

(b)  Rw  —  G  H 1 =  48  -f  9.6  +  19  =   76.6  sq.  ft. 

20        100 

3  G         WC 

(C)      Rw 1 1 36  +  19.2  +  19   =   74.2  sq.  ft. 

4  10       100 

owe 

(d)  Rs 1 1 =  24  +  19.2  +  9.5  =   52.7  sq.  ft. 

2         10        200 

2  W          C  2 

(e)  Rs  =  —  (G-  H 1 )  =  —  (48  +  9.6  +  19)   = 

3  20       100  3 
51  sq.  ft. 

G        W          C 

(f)  #*  = 1 1 =  24  +  9.6  +  9.5   =   43.1  sq.  ft. 

2         20       200 

Checking  these  Equations  51  and  53  we  have  Rw  —  76  sq.  ft. 
and  Rs  =  52  sq.  ft. 

102.  Direct-Indirect  Radiation: — This  system  of  heating 
is  used  in  some  homes  and  in  many  moderate  sized  school 
buildings.  It  has  the  simplicity  of  direct  radiation  with  cer- 
tain ventilating  possibilities  which  may  be  had  at  a  reason- 
able first  cost.  In  discussing  direct-indirect  heating,  how- 
ever, it  should  be  remembered  that  the  ventilating  feature 
of  the  system  is  very  erratic,  having  a  tendency  to  move  too 
much  air  when  the  wind  pressure  is  against  that  side  of  the 
building  where  the  radiator  is  located  and  too  little  air 
when  the  direction  of  air  movement  is  reversed.  The  re- 
quir  ment  of  a  constant  supply  of  1800  cubic  feet  of  air  per 
person  can  not  be  maintained  by  convection  processes  solely. 
The  reason  for  this  is  the  low  velocity  of  the  air  entering 
the  building  (even  in  some  cases  a  reversal  of  movement)  at 
times  when  the  air  pressure  is  reversed.  In  order  to  keep 
from  over  heating  the  room  with  too  much  direct-indirect 
radiation  (found  necessary  in  keeping  up  the  air  supply) 
some  reduction  must  be  made  from  the  usual  requirement  of 


HOT   WATER  AND   STEAM   HEATING  171 

ventilation  when  designing  this  type  of  system,  say  to  1200 
or  1500  cubic  feet.  Direct-indirect  radiation  should  always  be  used 
in  connection  with  inner  ivall  ventilating  stacks  and  preferably  those 
fitted  with  aspirating  coils.  Such  stacks  have  a  pull  on  the 
room  air  and  overcome  to  a  certain  extent  the  back  draft  of 
the  room  air  over  the  radiator. 

In  school  house  heating,  direct-indirect  radiation  is 
usually  installed  in  connection  with  direct  radiation.  The 
two  kinds  may  be  assembled  in  each  radiator  or  certain 
radiators  may  be  all  direct  and  others  all  direct-indirect  as 
preferred.  Ten  to  twelve  sections  of  the  standard  radiator 
are  usually  connected  to  one  wall  box.  Wall  boxes  are  made 
in  varying  sizes;  one  standard  form  being  sold  in  three  sizes 
— 8x24,  8x30  and  8x36  inches,  having  approximately  100,  125 
and  160  square  inches  net  area  respectively.  High  radiators 
should  be  used  because  of  the  chimney  effect  in  overcoming  back 
drafts.  Low  pressure  hot  water,  vacuum  or  atmospheric  steam  sys- 
tems should  be  used  with  caution  because  of  the  danger  of  freezing. 

In  estimating  direct-indirect  radiation  with  the  accom- 
panying duct  sizes,  it  may  be  done  by  either  one  of  two 
methods:  first,  estimate  the  direct-indirect  radiation  to  supply 
the  necessary  heat  to  warm  the  amount  of  ventilating  air 
desired  and  add  sufficient  direct  radiation  to  make  up  the 
balance  of  heat  for  the  calculated  heat  loss,  H;  second,  esti- 
mate the  direct  radiation  necessary  to  supply  H  and  add  50 
per  cent,  for  indirect  heat  given  to  the  entering  air,  then 
enclose  and  connect  to  wall  boxes  the  necessary  radiation 
for  direct-indirect  work. 

APPLICATION. — Assume  a  standard  recitation  room  in  a 
school  building  having  13"  brick  walls;  the  room  to  be  24 
ft.  x  30  ft.  one  side  and  one  end  exposed,  window  area  =  one- 
sixth  the  floor  area,  12  ft.  ceiling,  //  =  50000  B.  t.  u.,  and 
arrangement  of  seating  (excepting  8  feet  across  the  front 
of  the  room  reserved  for  instructional  purposes)  15  square 
feet  of  floor  space  per  pupil. 

ANALYSIS. — Number  of  pupils  35.  Amount  of  air  required 
for  ventilation  (say  1400  cu.  ft.  per  pupil)  =  49000  cu.  ft. 
per  hour.  Select  medium  sized  wall  box  125  sq.  in.  net  wind 
area.  With  favorable  conditions  we  may  expect  1  to  2  cu.  ft. 
air  per  min.  per  sq.  in.  net  wall  box  area  (air  velocity  2.5  to 
5  f.  p.  s.)  Call  this  1.5  cu.  ft.  We  have  125  X  1.5  X  60  = 
11250  cu.  ft.  per  hour  per  wall  box.  11250  -=-  1400  =  8  pupils 


172  HEATING  AND  VENTILATION 

supplied.  Pour  wall  boxes  8  in.  x  30  in.  will  approximately 
supply  all  the  pupils  at  the  rate  of  1400  cu.  ft.  per  person. 
These  theoretically  should  give  11250  x  4  =  45000  cu.  ft. 
air  per  hour.  Since  this  number  of  radiators  makes  a  good 
division  for  the  room,  the  same  number  of  radiators  may  be 
used.  In  the  direct-indirect  arrangement  just  mentioned, 
with  average  air  velocities,  air  temperatures  may  be  raised 
from  zero  to  125°  and  each  sq.  ft.  of  included  radiation  will 
give  off  approximately  375  B.  t.  u.  per  hour  (when  the  out- 
door air  is  below  zero  it  will  be  advisable  to  recirculate  part 
or  all  of  the  air).  The  heat  given  to  the  air  will  be  [45000  X 
(125  —  0)]  -f-  55  =  102272  B.  t.  u.  and  the  radiation  will  be 
102272  -h  375  =  273  sq.  ft.  =  four  radiators  68  sq.  ft.  each 
(approximately  160  cu.  ft.  of  air  per  sq.  ft.  of  radiator  sur- 
face). In  all  probability  these  would  be  taken  12  sec.  38-in. 

3  col.   60   sq.   ft.     With   60   sq.   ft.   in   each   radiator  the  total 
heat  given  off  to  the  air  in  the  room  will  be  approximately 

4  X    60    X    375    =   90000  B.  t.   u.     Of  this  amount  of  heat   56 
per  cent.   (50404  B.  t.  u.)   is  used  to  raise  the  temperature  of 
the  air  from  zero  to  70°   and  44  per  cent.    (39600  B.  t.  u.)   is 
used  to  raise  it  from  70°  to  125°.     This  latter  amount  will  be 
given  off  to  the  room  air  and  is  a  credit  to  the  heat  loss  H. 
50000  —  39600  =   10400  B.  t.  u.  to  be  supplied  by  direct  radia- 
tion.    10400    -~    250   =    41.6  sq.  ft.    =   8.3  sections,   38-in.   3-col. 
radiation.       Assuming     this     to     be     8     sections     and    divided 
equally  among  the  radiators  we  have  four  38-in.  3-col.  radi- 
ators each  consisting  of  12  sec.  direct-indirect  and  2  sections 
direct  radiation.     This  would  be  considered  a  fairly  satisfac- 
tory  arrangement.      The   direct-indirect  radiation   should   be 
installed  so  as  to  operate  as  such  on  outside  air  or  as  direct 
on  recirculated  air  if  desired. 

Under  the  second  method  suggested  find  50000  -T-  250  = 
200  sq.  ft.  of  direct  radiation  to  offset  H.  Add  50  per  cent.  = 
300  sq.  ft.  total  =  four  38-in.  3-col.  radiators  each  15  sec. 
divided  12  sec.  direct-indirect  and  3  se^p.  direct. 

Comparing  the  amount  of  radiation  obtained  by  the  first  method 
with  the  amount  required  if  heated  by  direct  radiation,  we  have 
direct  radiation  200  sq.  ft.   =    1.00 

f  direct-indirect  radiation  240  sq.  ft.    =    1.20 

Combined   / 

I    direct  radiation        -         -  40  sq.  ft.   =      .20 


HOT    WAT1SII   AND    STEAM   HEATING 


173 


103.  Gravity  Indirect  Radiation: — This  provides  one  of 
the  most  satisfactory  systems  of  heating.  In  all  essentials 
it  compares  with  the  furnace  system,  with  the  furnace  re- 
placed by  individual  steam 
or  hot  water  radiators. 
(See  Fig-.  96).  It  is  an  im- 
provement over  the  direct- 
indirect  system  in  that 
there  is  a  fairly  constant 
air  movement  to  the  room. 
Radiators  of  either  the  ex- 
tended pin  or  ribbed  type 
are  used.  Some  of  the 
standard  sizes  are  given  in 
Table  XIV. 

The  indirect  radiator 
should  be  set  20  to  24 
inches  above  the  water  line 
of  the  boiler.  There  should 
be  a  clearance  of  10  inches 
at  the  top  and  8  inches  at 


iiiiiiiiiiiiiiiiiiiiiiiilHiiiiiiii 
III! 


Fig.  96. 


the  bottom  between  the  casing  and  the  radiator,  for  cold  air 
and  warm  air  chambers,  but  the  casing  on  the  sides  and  ends 
should  be  close  to  the  radiator.  The  radiators  are  suspended 
from  the  joiste  and  connected  to  the  steam  and  return  mains 
in  such  a  way  as  to  permit  free  expansion  and  contraction. 
All  pipes  must  be  graded  for  free  drainage  to  the  boiler. 

TABLE  XIV. 


Per- 

Sanitary 

fec- 

Gold Pin 

School 

tion 

Pin  Indirect 

Pin 

Pin 

Sq.   ft.  H.  S 

per  see. 

12 

15 

20 

15 

20 

10 

10 

15 

20 

L 
H 

36 
9 

36 
11% 

36 

15% 

36% 

n% 

36i/8 
15% 

36% 
$1 

36% 

8% 

36% 
11% 

36 

14% 

0 

&% 

3% 

3% 

4 

4 

2% 

3 

3 

8% 

Pipe  sizes  may  be  the  same  as  those  used  on  any  two-pipe 
radiator  having  equivalent  condensation.  Low  radiator  sec- 
tions (7i  =  6  to  10  inches)  are  recommended  for  residences 
and  offices.  High  radiators  (h  —  10  to  15  inches)  are  recom- 
mended for  schools. 


174  HEATING  AND   VENTILATION 

To  determine  the  amount  of  air  circulated  per  hour,  read 
Arts.  49-51.  In  residences  and  offices,  air  as  a  heat  carrier 
will  be  sufficient.  In  schools  and  auditoriums  there  will  be 
an  excess  of  air  for  ventilation.  Where  this  is  true  the  tem- 
perature of  the  air  leaving  the  radiator  should  be  corre- 
spondingly below  what  it  would  be  if  only  heating  were  con- 
sidered. (See  Art,  52). 

The  lowest  temperature  of  the  entering  air  may  be  taken  zero. 
At  lower  temperatures  part  or  all  of  the  air  should  be  recir- 
culated.  The  temperature  of  the  air  leaving  the  radiator  depends 
upon  the  velocity  of  movement  over  the  radiator. 

Table  XV,  from  experiments  by  J.  R.  Allen,  cols.  2  and  3, 
gives  air  temperature  rise  in  passing  over  the  radiator. 
TABLE  XV. 


B.  t.  u.  transmitted 

Cubic  feet 

Rise  in 

Pounds  of  steam 

per  sq.  ft.  of 

of  air 
passing 
per  sq.  ft. 

temperature 
of  the  air 

Condensed  per  sq.  ft. 
of  radiation 

radiation  per  degree 
difference  in  temp, 
between  steam  and  air 

of  radia- 

tion 
per  hour 

Stand- 
ard pin 

Long 
pta 

Standard 
pin 

Long 
pin 

Standard 
pin 

Long 
pin 

50 

147 

140 

0.125 

0.150 

0.80 

0.95 

75 

143 

137 

0.170 

0.210 

1.17 

1.27 

100 

140 

135 

0.240 

0.260 

1.51 

1.60 

125 

138 

132 

0.295 

0.310 

1.85 

1.90 

150 

135 

129 

0.355 

0.360 

2.22 

2'.  20 

175 

132 

126 

0.410 

0.405 

iir>7 

2.47 

200 

130 

123 

0.470 

0.450 

2.90 

2.72 

225 

127 

120 

0.530 

0.490 

3.25 

3.00 

250 

123 

118 

0.585 

0.530 

3.60 

3.20 

•    275 

121 

115 

0.645 

0.570 

3.90 

3.40 

300 

119 

112 

0.700 

0.610 

4.22 

3.60 

In  the  design  of  indirect  heating  systems  there  are  cer- 
tain approximate  values  which  may  be  recommended  as  rep- 
resenting fairly  standard  practice.     These  values  which  fol- 
low may  be  used  in  connection  with  Table  XV. 
Cu.  ft.  of  air  per  sq.  ft.  of  radiation 

(residence)     steam   150  water  100 

K  for  residence  heating  2.2 

Cu.  ft.  of  air  per  sq.  ft.  of  radiation 

(schools)    "        200         "        133 

K  for  school  heating  2.6 

Temperature  of  air  entering  radiator zero 

Temperature  of  air  leaving  radiator 

(residence)   100,   125   and   150 


HOT   WATER   AND  STEAM  HEATING  175 

Sq.  ft.  of  radiation  determined  by  Equation  56  or  57 

H' 
Rs   =  (56) 


/  t     +     to    \ 

*(•'-—  -) 


(57) 


2  2 

Where  terms  are  as  stated  in  Art.  101. 
Sq.  in.  of  flue  area  per  sq.  ft.  of  rad.  Steam     Water 

Height  between  c.  of  rad.  and  c.  of  reg.  5  ft.  2.00  1.33 

10  ft.  1.40  .90 

"  20  ft.  1.00  .66 

Select  type  of  radiator  from  catalog  data. 

Indirect  radiators  are  usually  arranged  to  permit  recir- 
culation  of  the  air  from  the  house  when  desired.  For  other 
information  on  recirculating  ducts,  registers,  etc.,  see  fur- 
nace heating. 

APPLICATION  1. — In  Art.  62,  the  Living  Room  (H  —  15267) 
and  Chamber  1  (H  =  10583)  are  to  be  supplied  with  indirect 
steam  heat,  design  the  heaters  and  heat  lines. 

S.OLUTION. — Assume  to  =  O;  t  =  125  and  f«  =  220;  then  for 
the  Living  Room 

55  X  15267 

Q   (Eq.  33)    =  -  -  =    15267 

125  —  70 

15267  X   (70  —  0) 

H'  (Eq.  30)   =   15267   +  -  =   34698 

55 

34698 
Rs   (Eq.  56)    =  =   100  sq.  ft. 


/  125  +  0  \ 

?  2   I    220 I 

V  2         / 


Efficiency  of  radiator  =  2.2   (220  —  62.5)   =  346.5  B.  t.  u 

Amount  of  circulating  air  =  100  X   150  =  15000  cu.  ft. 

Compare  this  with  calculated  value  of  Q. 

Check  amount  of  indirect  radiation  with  direct  radiation, 
Art.  101,  Eq.  53.  This  shows  an  increase  of  (100  —  61)  4- 
61  r=  64  per  cent,  above  the  calculated  direct  radiation  for 
the  same  room. 


176  HEATING  AND  VENTILATION 

Square  inches  warm  air  duct  area  =  2   X   100   =   200. 
Square  inches  cold  air  duct  area   =    200    X    .8    =   160. 
For  Chamber  1,  with  temperatures  as  before 
55  X  10583 


125  —  70 


—  10583 


10583  X  (70  —  0) 

U'  =  10583  +  -  -  =  24143 

55 

24143 

=  70  sq.  ft. 


(125+0    \ 
220 I 


Efficiency  of  radiation  =  346.5  B.  t.  u. 

Check  amount  of  circulating  air,  70   X    150  =  10500  cu.  ft. 

Compare  this  with  Q. 

Check  indirect  radiation  with  direct  radiation,  66  per 
cent,  increase. 

Square  inches  of  warm  air  duct  area  =   1.25   X    70   =   88 

Square  inches  of  cold  air  duct  area      =      88   X     .8   =  70 

APPLICATION  2.  —  In  Art.  102,  a  school  room  24  x  30  ft.  has 
a  heat  loss  of  50000  B.  t.  u.  and  has  35  pupils.  It  is  required 
that  this  room  be  heated  by  indirect  radiation,  design  the 
heaters  and  heat  lines. 

SOLUTION.  —  Q  =  35   X   1800  =  63000;  to  =  0;  /*   —   227. 

50000  X  55 

*  =  -  -  +  70  =   113.6  say  114°. 

63000 

H'  -  50000   +   63000   X    1.27   =   130180. 

130180 
Rs   —  -  =   295  sq.  ft. 

/  114  +  0    \ 

2.6227  --  -- 


Efficiency  of  radiator  =   442  B.  t.  u. 

Check  amount  of  circulating-  air,  63000  4-  295  =  213  cu.  ft. 
per  sq.  ft.  radiation. 

Check  amount  of  indirect  radiation  with  direct  radiation  for  the 
same  room  and  find  direct  =  200,  indirect  =  295;  approximately 
1.00  :  1.50. 

104.  Aspirating  Coils:  —  For  the  most  efficient  service, 
direct-indirect  and  indirect  heating  should  be  accompanied 
by  a  positive  ivithdrawal  of  the  air  from  the  rooms  through 
ventilating  ducts.  This  is  true  especially  in  the  heating  of 
school  buildings.  Individual  electric  driven  fans  may  be 


HOT   WATER   AND    STEAM   HEATING 


177 


housed  in  the  vent  ducts  or  the  vents  may  be  gathered  to- 
g-ether in  the  attic  and  housed  in  around  one  exhaust  fan, 
but  these  plans  require  extra  care  in  installing  and  are  ex- 
pensive in  first  cost.  Furthermore,  in  many  places  electric 
power  can  not  be  had.  In  such  places  indirect  radiation 
(aspirating  coils)  may  be  placed  in  the  vents  as  shown  by 
Fig.  97  and  the  heat  given  off  will  produce  convection  air 
currents  which  insure  a  positive 
withdrawal  of  the  room  air.  This 
is  not  an  efficient  method  of  pro- 
ducing draft,  in  fact  any  other 
workable  method  should  be  em- 
ployed where  possible. 

In  installing  aspirating  coils 
they  should  each  be  piped  direct 
from  the  boiler  room.  The  valves 
should  be  located  in  the  boiler 
room  and  should  be  under  the 
control  of  the  boiler  attendant. 
When  the  rooms  are  not  occupied, 
steam  should  be  cut  out  of  the 
coils  and  the  vent  dampers  close:! 
to  avoid  depleting  the  room  of 
warm  air.  When  coils  are  cut  off 
they  should  be  drained  to  avoid 
freezing. 

The  amount  of  radiation  to  install  in  each  vent  flue 
varies  in  different  localities.  Fairly  satisfactory  results 
seem  to  be  obtained  with  two  vents  to  each  room  (25  x  30  x 
12  ft.)  and  30  to  40  square  feet  of  cast  iron  indirect  radiation 
in  each  vent.  For  sizes  of  vent  ducts  above  heaters  see  cor- 
responding sizes  in  furnace  heating. 

1O5.  Greenhouse  Heating: — In  estimating  greenhouse 
radiation  the  problems  are  essentially  different  from  those  in 
ordinary  house  radiation.  In  greenhouses  glass  surface  is 
large,  wall  surface  is  small  and  air  circulation  is  compara- 
tively less.  The  rational  equation  for  heat  loss,  therefore, 
has  less  to  do  with  volume  and  except  in  unusual  cases  may 
be  considered  to  have  but  two  terms — glass  and  wall.  Where 
volume  is  accounted  for,  calculate  H  as  in  Chap.  III.  Instead 
of  ordinary  cast  iron  radiation,  the  radiating  surfaces  are 
•wrought  iron  or  steel  pipes  l1^-,  1%-  or  2-inch  diameter  (or 


Fig.  97. 


178 


HEATING  AND   VENTILATION 


cast  pipes  2l/2-  to  4-inch  diameter)  assembled  as  coils  with 
manifold  headers.  The  values  of  K  for  these  coils  may  be 
found  in  Art.  92.  Although  test  values  run  as  high  as  2.65 
for  single  horizontal  pipes  it  is  a  safe  plan  because  of  the 
dirt  deposits  on  and  in  the  pipes,  to  allow  an  average  value 
of  not  to  exceed  2.2  for  all  wrought  iron  or  steel  coils  and 
1.8  for  all  cast  iron  coils.  Find  //  by  Equation  26  (or  27), 
using  only  glass  and  wall  equivalent  and  substitute  in  Equa- 
tions 49  and  50.  For  all  practical  purposes  H  =  (G  +  .25 
Eq.  W)  70. 

Assuming  wrought  or  steel  coils  and  zero  weather 
H 


2.2  (170  —  70) 
H 


-   .0045  // 


-   .0030  // 


(58) 


(59) 


2.2  (220  —  70) 

If  the  desired  indoor  temperature  is  other  than  70°,  this 
temperature  should  be  substituted  for  70  in  the  equation. 
Assuming  t'  =  70  we  have  Rw  —  .32  (G  +  .25  Eq.  W)  and 
R*  =  .21  (G  +  .25  Eq.  W) ;  =  one  square  foot  of  H.  W.  radiation 
to  3.1  square  feet  of  equivalent  glass  area  and  one  square  foot  of 
steam  radiation  to  4-8  square  feet  of  equivalent  glass  area. 
Table  XVI  (Model  Boiler  Manual)  shows  the  amount  of  sur- 
face for  different  interior  temperatures  and  different  tem- 
peratures of  the  heating  medium. 

TABLE  XVI. 


Temperature  of  water  In  heating  pipes 

Steam 

air  in 

140°      |      160°       |      180°       |      200° 

Three  Ibs.  pressure 

house 

Square  feet  of  glass  and  its  equivalent  proportioned  to  one 
square  foot  of  surface  In  heating  pipes  or  radiator 

4C° 

4.33 

5.25 

6.66 

7.69 

8.0 

10.00 

45° 

3.63 

4.65 

5.55 

6.66 

7.5 

8.50 

50° 

3.07 

3.92 

4.76 

5.71 

7.0 

7.40 

55° 

2.63 

3.39 

4.16 

5.00 

6.5 

6.60 

60° 

2.19 

2.89 

3.63 

4.33 

6.0 

5.90 

65° 

1.86 

2.53 

3.22 

3.84 

5.5 

5.20 

70° 

1.58 

2.19 

2.81 

3.44 

5.0 

4.80 

75° 

1.37 

1.92 

2.50 

3.07 

4.5 

4.30 

807 

1.16 

1.63 

2.17 

2.73 

4.0 

3.90 

85° 

.99 

1.42 

1.92 

2.46 

3.5 

3.50 

This  table  is  computed  for  zero  weather;  for  lower  tem- 
peratures add  1*72  per  cent,  for  each  degree  below  zero.     The 


HOT  WATER   AND    STEAM   HEATING 


179 


last  column  was  calculated  from  Equation  50  (K  =  2.2)  and 
added  for  purpose  of  comparison. 

Empirical  rules  for  greenhouse  radiation  are  sometimes 
given  in  terms  of  the  number  of  square  feet  of  glass  surface 
heated  by  one  lineal  foot  of  l^-inch  pipe.  One  such  rule  is 
— "one  foot  of  1^4 -inch  pipe  to  every  2^  square  feet  of  glass, 
for  steam;  and  one  foot  of  l^-inch  pipe  to  every  1%  square 
feet  of  glass,  for  hot  water,  when  the  interior  of  the  house 
is  70°  in  zero  weather."  Great  care  should  be  exercised  in 
rating  and  selecting  the  boilers  and  heaters.  It  is  well  to 
remember  that  the  severe  service  demanded  by  a  sudden 
change  in  the  weather  is  much  more  difficult  to  meet  in 
greenhouses  than  in  ordinary  structures,  and  that  a  liberal 
reserve  in  boiler  capacity  is  highly  desirable. 

Both  steam  and  hot  water  systems  are  in  general  use. 
Where  continuous  heat  may  be  obtained  throughout  the 
night  from  a  central  plant  a  steam  system  is  very  desirable. 
In  the  isolated  plant  where  the  steam  pressure  drops  during 
the  night  time  a  hot  water  system  will  give  more  satisfac- 
tory service  in  cold  weather  because  it  guarantees  a  better 
circulation  of  heat  throughout  the  night. 

The  same  rules  apply  in  running  the  mains  and  risers  as 
apply  in  the  ordinary  hot  water  and  steam  systems.  In 
greenhouse  work  the  head  of  water  in  a  water  system  is 
necessarily  very  low  and  tends  to  make  the  circulation 
sluggish,  but  with  sufficient  pipe  area  to  reduce  the  friction 
a  hot  water  open  tank  system  having  a  very  low  head  may 
be  made  to  work  satisfactorily.  In  some  houses  the  coils 
are  run  along  the  wall  below  the  glass  and  supported  on 
wall  brackets;  in  others  they  are  run  underneath  the 
benches  and  supported  from  the  benches  with  hangers.  In 
greenhouses  with  very  large  exposure  there  are  sometimes 
required  both  wall  and  bench  coils,  also,  a  certain  amount  in 


RISE 

WATER  OP  STEAM 


Fig".  98. 


180  HEATING  AND  VENTILATION 

the  center,  6  to  7  feet  from  the  floor.  In  all  of  these  piping- 
layouts  it  is  necessary  that  as  much  rise  and  fall  be  given 
to  the  pipes  as  possible.  Fig.  98  shows  two  systems  of  pipe 
connections,  one  where  the  steam  or  flow  enters  the  coils 
from  above  the  benches  and  the  other  where  it  enters  from 
below,  the  return  in  each  case  being  at  the  lowest  point. 
These  bench  coils  could  be  run  along  the  wall  with  equal 
satisfaction. 

APPLICATION. — Given  an  even-span  greenhouse  25  ft.  wide, 
100  ft.  long  and  5  ft.  from  ground  to  eaves  of  roof,  having 
the  slope  of  the  roof  with  the  horizontal  35°.  The  ends  to 
be  glass  above  the  eaves  line.  What  amount  of  hot  water 
radiation  with  average  water  temperature  170°,  interior 
temperature  70°  and  outside  temperature  0°,  and  what 
amount  of  low  pressure  steam  radiation  should  be  installed? 

Length  of  slope  of  roof  =  12.5  -f-  cos.  35°  —  15.25.  Area 
of  glass  =  15.25  X  100  X  2  +  2  X  12.5  X  8.8  =  3270  sq.  ft. 
Area  of  wall  =  5  X  100  X  2  +  5  X  25  X  2  =  1250  sq.  ft. 
Glass  equivalent  =  3270  +  .25  X  1250  =  3582.5  sq.  ft.  Rw  = 
.32  X  3582.5  =  1146  sq.  ft.  R*  =  .21  X  3582.5  =  752  sq.  ft. 
From  Table  XVI.  Rw  =  3582.5  -=-  2.81  =  1270  sq.  ft.  R»  = 
3582.5  -T-  5  =  716  sq.  ft.  *Check  with  last  column  of  Table 
XVI. 

REFERENCES. — Jour.  A.  S.  H.  &  V.  E.  Heating  a  Conserva- 
tory and  Greenhouse,  July  1916,  p.  29.  Metal  Worker.  Design 
of  Greenhouse  Heating  Plants,  July  9,  1915,  p.  44.  Heating 
Equipment  for  Large  Greenhouse,  Jan.  1,  1915,  p.  66.  Domes- 
tic Engineering.  The  Hot  Water  Heating  in  Highland  Park 
Greenhouse,  Sept.  21,  1912,  p.  292. 

106.  The  Theoretical  Determination  of  Pipe  Sixes: — The 
theoretical  determination  of  pipe  sizes  for  small  hot  water 
and  steam  systems  has  always  been  more  or  less  unsatisfac- 
tory because  of  the  difficulty  in  estimating  the  friction  of- 
fered by  different  combinations  of  piping.  The  following 
analysis  is  illustrative  and  does  not  account  for  friction. 

Assume  a  hot  water  system,  Figs.  101-104,  having  water 
temperatures  entering  and  leaving-  the  radiators  180°  and 
160°  respectively.  Since  one  pound  of  water  in  passing 
through  each  radiator  gives  off  20  B.  t.  u.,  the  radiators  in 
the  Living  Room  (91  sq.  ft.)  and  Chamber  2  (70  sq.  ft.)  will 
require  91  and  71  gallons  of  circulating  water  per  hour 
(check  the  values),  or  approximately  one  gallon  of  water  per 


HOT  WATER  AND    STEAM   HEATING  181 

square  foot  of  radiating  surface  per  hour.  This  is  a  general  state- 
ment which  will  be  true  for  any  low  pressure  hot  water 
system  with  20  degrees  temperature  drop.  With  the  amount 
of  water  required  per  hour  obtain  the  velocity  due  to  the 
unbalanced  columns  and  find  by  division  the  area  of  the  pipe. 
Assume  the  radiator  in  the  Living  Room  to  have  a  5-ft. 
static  head  and  that  in  Chamber  2  a  15-ft.  head.  Having 
the  water  temperature  in  the  flow  risers  180°  and  in  the  re- 
turn risers  160°  (good  values  in  practice),  the  heated  water 
in  the  flow  risers  weighs  60.5567  pounds  per  cubic  foot,  while 
that  in  the  return  risers  weighs  60.9697  pounds  per  cubic 

W  —  W 

foot.     The  motive  force  is  f  =  0   X   -  — ,  where  g  is  the 

W  +  W 

acceleration  due  to  gravity,  TF  is  the  specific  gravity 
(weight)  of  the  cooler  column  and  W  is  the  specific  gravity 
(weight)  of  the  warmer  column.  Substitute  f  for  g  in  the 
velocity  equation  and  obtain 


(60) 
W 

Inserting  values  W,  W  and  h  =  (5  and  15)  feet,  we  have 
v  =  1.05  f.  p.  s.  (Living  Room)  and  1.8  f.  p.  s.  (Chamber  2). 
Velocities  for  any  other  height  of  column  and  for  other  tem- 
peratures may  be  obtained  in  like  manner.  Reducing  the  91 
and  71  gallons  to  cubic  inches  and  dividing  by  the  velocity 
per  hour  in  inches  gives  .46  sq.  in.  and  .21  sq.  in.  respec- 
tively. Since  pipe  sizes  are  measured  on  the  internal  diam- 
eter these  values  are  equivalent  to  pipes  of  %-  and  ^-inch 
respectively.  For  the  determination  of  pipe  sizes,  friction  included, 
see  Art.  197.  The  application  of  friction  equations  to  pipes 
of  4  inches  or  more  in  diameter  is  very  satisfactory  but  for 
small  pipes,  such  as  are  found  in  the  average  house  heating 
plant,  it  is  still  the  custom  to  use  tables  of  sizes  based  upon 
what  experience  has  shown  to  be  good  practice.  Such  tables 
may  be  found  in  the  Appendix.  From  Table  34  we  find  the 
branches  and  risers  to  the  two  radiators  under  consideration 
to  be  l^-  and  1-inch  respectively. 

In  steam  systems  where  the  heating  medium  is  a  vapor  and 
subject  in  a  lesser  degree  to  friction,  the  discrepancy  be- 
tween the  theoretical  and  the  practical  sizes  of  a  pipe  is  not 
as  great  as  in  hot  water.  Each  pound  of  steam  at  220°  in 
condensing  gives  off  about  970  B.  t.  u.  To  supply  the  heat 


182 


HEATING  AND  VENTILATION 


loss  of  the  Living  Room,  15267  B.  t.  u.,  requires  15.8  pounds 
of  steam  per  hour  =  .26  pounds  of  steam  per  square  foot  of 
radiation.  As  a  general  statement  use  one-fourth  of  a  pound  of 
steam  per  square  foot  of  direct  radiation  per  hour.  To  check  this 
statement,  each  square  foot  of  steam  radiation  gives  off  250 
B.  t.  u.  per  hour  and  will  condense  250  ^  970  =  .258  pounds 
of  steam. 

The  volume  of  the  steam  per  pound  at  the  usual  steam 
heating  pressure  17  to  18  pounds  absolute  is  23  cubic  feet. 
Since  the  above  radiator  requires  15.8  pounds  per  hour  there 
will  be  needed  23  X  15.8  =  363  cubic  feet  per  hour.  With 
the  velocity  of  the  steam  in  the  pipe  lines  15  feet  per  second 
(900  ft.  per  min.  about  one-seventh  that  allowed  for  power 
plant  machinery.  Taken  as  a  fair  approximation  for  small 
pipes)  the  area  of  the  pipe  will  be  363  X  144  -^  54000  = 
.97  sq.  in.  =  1%-in.  diameter.  For  two-pipe  connections  a 
1-inch  pipe  would  be  considered  good  practice,  but  for  one- 
pipe  connections  where  the  condensation  is  returned  against 
the  steam,  a  l^-inch  pipe  would  be  required. 

See  Tables  38,  39,  40  and  41,  Appendix,  for  sizes  and 
capacities  of  pipes  carrying-  steam.  For  a  discussion  of 
steam  pipe  sizes  by  rational  equation,  including  friction,  see 
Art.  197. 

107.      Proportion! UK   Pipe   Sizes   for  a   Heating   System; — 

Begin  at  the  farthest  radiator  and  proceed  toward  the  boiler 
as  shown  in  the  following  tabulations. 


Fig-.  99. 


HOT   WATER  AND   STEAM   HEATING 


183 


Basement  Main  Two-Pipe  Hot  Water  System   (Fig.  99). 
TABLE   XVII. 


L.  P.  =  Low  Pressure  Open  Tank  System.    H.  =  Honeywell  System. 

Branch 

Branch 

Cn      ff 

from  Had. 

Riser 

from  Main 

Main 

L.  P. 

H. 

Iy.  P. 

H. 

L.  P. 

H. 

L.  P. 

H. 

60 

1 

% 

A  1 

A    % 

80* 

1% 

1% 

B  iy2 

B  1% 

C  2 

1% 

140 

D  2y2 

D  2 

60 

1 

% 

E  1 

E     % 

70 

1 

% 

F  iy2 

F  1 

70 

1% 

1 

Giy4 

G  1 

H  1V2 

iy2 

340 

I  2% 

1  2y2 

80 

1 

% 

j  i 

J     % 

70 

1 

% 

K  1% 

K  1 

100 

1% 

1 

L  1% 

L  1 

M  2 

2 

590 

N  3 

N  2y2 

End  of  supply  line,  first  floor  radiator  given  advantage 
Return  branches  same  as  supply  branches 
Return  Main  reversed. 


o 

P 

Q 

L.  P. 
2 

H. 

L.  P. 

2i/2 

H. 

L.  P. 

H. 

2 

21/2 

3 

2% 

Basement  Main  Two-Pipe  Steam  System. 
Sealed  returns.      (See  Fig-.  99). 


TABLE  XVIII. 


Branch 

Branch 

SQ    ft 

from  Rad. 

Riser 

from  Main 

Main 

S 

R 

S       |       R 

S 

R 

S 

R 

60 

1% 

A  1% 

1 

80 

11/2 

B  1% 

1 

C  2 

iy2 

140 

D  2% 

Q2 

GO 

1% 

E  1% 

1 

70 

1% 

F  iy2 

1% 

70 

1% 

G  1% 

i 

H  2 

iy2 

340 

I  3 

P  2 

80 

v& 

J  1% 

i 

70 

1% 

K  1% 

1% 

100 

iy2 

1% 

L  1% 

1% 

M  2 

1% 

590 

N  3 

0  1% 

184 


HEATING  AND   VENTILATION 


^    73  Sailer 

Fig".  100. 

Basement  Main  One-Pipe  Steam  System   (Fig.  100). 
TABLE  XIX. 


Sq.  ft. 

Branch 
from  Rad. 

Riser 

Branch 
from  Mam 

Main 

60 

iy2 

A  iy2 

80 

iy2 

B  1% 

C  2 

140 

D  2% 

60 

m 

E  iy2 

70 

1X£ 

~F  2 

70 

iy2 

G  iyz 

H  2 

340 

I  3 

80 

iy2 

T  1  1>4 

70 

iy2 

K  2 

100 

2 

L  2 

M  2^ 

590 

N  3 

Return  line  to  boiler  same  as  dry  return  for  two-pipe 
system,  in  this  case  2-inch. 

108.  Pitch  of  Mains: — The  pitch  of  the  mains  should  be 
not  less  than  1  inch  in  10  feet  for  hot  water  systems  and  1  inch  in 
30  feet  for  steam  systems.  Greater  pitches  than  these  are  desir- 
able but  are  not  always  practicable.  In  hot  water  plants  the 
one-pipe  main  has  its  highest  elevation  above  the  boiler  and 
drops  to  the  far  end  of  the  line,  with  the  lowest  point  where 
it  enters  the  boiler,  the  two-pipe  basement  main  and  return 
each  pitch  upward  from  the  boiler  to  the  end  of  the  run  and 
the  attic  main  has  its  highest  point  at  the  top  of  the  attic 
riser.  The  two  pipe  systems,  both  basement  and  attic  mains, 
should  have  the  supply  and  return  reversed,  i.  e.,  the  return 


HOT  .WATER  AND   STEAM   HEATING  185 

should  begin  at  the  first  radiator  served  by  the  supply.  In 
steam  plants  the  supply  main  pitches  downward  toward  the 
far  end  of  each  run,  the  highest  point  being-  above  the  boiler. 
The  return  main  pitches  downward  from  the  end  of  each  run 
toward  the  boiler. 

109.  Location  and  Connection  of  Radiators: — In  locating 
radiators,  it  is  usual  to  place  them  along  the  outside  or  ex- 
posed  walls   and   when   allowable,   under   the   windows.      This 
is    probably    the    best    location    although    some   difference    of 
opinion   has   been   expressed   on   this  point.      When   so   placed 
the  cold  current  of  air  from  the  window  interferes  with  the 
warm    upward    current   from   the   radiator   and   breaks   it    up. 
A  series  of  tests  .reported  in  the  Journal  of  the  A.  S.  H.  and 
V.    E.,    July    1916,    page    65,    by    a    special    committee    of    the 
society,  shows  that  next  to  the  center  of  the  room  the  floor 
line  near  the  outside  wall  is  the  most  effective  location.     In 
buildings    of    several    stories,    the    radiators    should    be    ar- 
ranged as  far  as  possible   in   tiers,  one  vertically  above  an- 
other,  thus   reducing   the    number   of  risers   and   offsets.      In 
one-pipe   and   two-pipe   steam   systems   any   number   of  radi- 
ators may  be  connected  to  the  same  riser,  providing  the  riser 
is   proportioned   to   the   radiation   supplied.      In   the   two-pipe 
systems  a  water  seal  between  each  radiator  and  the  return 
riser  is  advisable.     This  insures  each  radiator  to  be  an  inde- 
pendent unit   in   its  action.     In  two-pipe  hot  water  systems 
several   radiators  may  have   common   flow  and   return  risers 
as  in  steam  systems  providing  the  risers  are  carefully  pro- 
portioned to  the  radiation.     This  is  not  always  a  safe  plan. 
Under   such   an   arrangement   the   upper  radiators   frequently 
have  the  advantage  and  rob  the  lower  radiators.     To  be  -sure 
upon  this  point,  either  one  of  two  methods  may  be  employed: 
(1)    offset    the    riser    (See    radiators    C    and   D,    Fig.    50);    (2) 
isolate  the  returns  (See  radiators  A  and  B,  Pig.  49). 

The  connections  from  the  risers  to  the  radiators  should 
be  slightly  pitched  for  drainage.  They  may  be  run  along 
the  ceiling  below  the  radiator  or  above  the  floor  behind  the 
radiator.  Connections  should  be  at  least  2  feet  long  to  give 
flexibility  for  the  expansion  and  contraction  of  the  riser. 
For  sizes  of  radiator  connections  see  Table  41,  Appendix. 

110.  General  Application: — Figs.    101-104   show   an   illus- 
trative layout  of  a  hot  water  plant    (See   residence  Art.   62). 
Because  of  the  similarity  between  hot  water  and  steam   in- 


186  HEATING  AND  VENTILATION 

stallations,  the  former  only  will  be  outlined.  In  making 
the  layout  of  such  a  system,  first  locate  the  radiators  in  the 
rooms.  This  should  be  done  with  the  advice  of  the  owner 
who  may  have  particular  uses  for  certain  spaces  from  which 
radiators  must  be  excluded.  Calculate  the  heat  loss  for  each 
room,  including  exposure  losses,  ventilation  losses,  etc.,  and 
tabulate  the  results  (See  first  column  Table  XX.  Taken 
from  Table  XII).  Calculate  the  square  feet  of  radiation 
(Equation  51)  and  select  the  type,  height  and  number  of  sec- 
tions of  each  radiator  from  Table  XIII.  Check  the  radiator 
lengths  and  determine  whether  or  not  a  radiator  of  such 
length  will  fit  into  the  chosen  space.  If  this  can  not  be  done, 
a  radiator  of  greater  height  or  number  of  columns  must  be 
selected.  Branches  from  main  to  riser  and  riser  sizes  are 
usually  the  same  although  on  a  long  branch  it  may  be  found 
necessary  to  put  in  a  branch  one  size  larger  than  the  riser. 
Also,  the  branch  from  the  riser  to  the  radiator  and  the  radi- 
ator connection  sizes  are  usually  the  same  excepting  where 
there  may  be  unusual  conditions  to  meet,  in  which  case  the 
branch  may  be  made  one  size  larger  than  the  standard  con- 
nection. For  commercial  sizes  see  Tables  38  and  40,  Appen- 
dix. Column  in  Table  XVII  marked  "Radiators  installed" 
should  read  "number  of  sections,  height  in  inches  and  number 
of  columns"  (See  Living  Room  =  18-38-3). 

Locate  the  risers  on  the  second  floor  plan  and  transfer 
these  locations  to  the  first  floor  and  basement  plans.  Treat 
the  first  floor  risers  in  a  similar  manner.  The  basement 
plan  will  then  show  by  small  circles  the  location  of  all  risers. 
This  arrangement  will  aid  greatly  in  the  planning  of  the 
basement  mains.  The  principal  features  in  the  layout  of  the 
basement  mains  should  be  simplicity  and  directness.  If  the 
riser  positions  show  approximately  an  even  distribution 
around  the  basement,  it  may  be  advisable  to  run  the  main 
as  a  complete  circuit  system.  If  the  riser  positions  show 
aggregations  at  two  or  three  localities,  two  or  three  mains 
running  directly  to  these  localities  are  the  most  desirable. 
As  an  illustration  the  basement  plan  shows  three  clusters 
of  riser  ends,  one  under  the  kitchen,  another  under  the  study, 
and  a  third  along  the  west  side  of  the  house.  This  condition 
immediately  suggests  three  supply  mains.  That  toward  the 
north  supplies  the  bath,  chamber  4  and  the  kitchen,  a  total 
of  161  square  feet.  Being  approximately  13  ft.  long,  a  iy2- 


HOT   WATER  AND   STEAM   HEATING 


187 


inch  main  will  carry  the  radiation.  That  toward  the  east 
supplies  chamber  1,  the  hall  and  the  study,  a  total  of  225 
square  feet,  which  can  be  carried  by  a  2-inch  pipe.  That 
toward  the  west  side  of  the  house  supplies  chamber  2,  cham- 
ber 3,  the  living"  room  and  the  dining  room,  a  total  of  277 
square  feet,  which  should  have  a  2-inch  main. 

In  hot  water  work,  as  well  as  in  steam,  it  is  customary 
to  connect  supply  branches  (especially  first  floor  branches) 
from  the  top  of  the  mains,  thus  aiding  the  natural  circula- 
tion. If  this  is  not  possible  connect  at  45  degrees.  With  a 
short  nipple,  a,  45  degree  elbow  and  a  horizontal  run  of  2  to 
3  feet  this  arrangement  has  sufficient  flexibility  to  avoid 
expansion  troubles.  First  floor  radiators  and  those  farthest 
from  the  boiler  should  be  given  the  advantage  of  top 
branch  connections  and  larger  proportional  pipe  sizes. 

In  the  selection  of  the  boiler  estimate  the  grate  size  from 
the  total  heat  loss  and  check  by  the  catalog  rating  in  square 
feet  of  radiation.  With  soft  coal  at  13000  B.  t.  u.  per  pound,  an 
efficiency  of  60  per  cent,  and  5  pounds  of  coal  per  square 
foot  of  grate  per  hour  there  will  be  needed  (110574  X  144)  -f- 
.60  X  5  X  *3000  =  408  sq.  in.  grate  area.  Adding  50  per 
cent.  (Art.  100)  for  soft  coal  gives  612  sq.  in.  This  agrees 
with  Am.  Rad.  boiler  W-19-6,  1250  sq.  ft.  rating.  Checking 
radiation  equivalent  =  663  sq.  ft.  calculated  radiator  surface  + 
25%  mains,  risers,  etc.,  —  829  sq.  ft.  total  radiation  +  50  per 
cent.  —  1236  sq.  ft. 

TABLE  XX. 


Heat 
loss,  H 
from 
Table 
XII 

Rad. 

Surface 

R  = 
.006H 

Radia- 
tors 
installed 

Length 
of  Rad. 
installed 

Branches 
and 
Risers. 
Supply 
and 
Return 

Rad. 

connec- 
tion 

Living-  R.  
Dining  R.  
Study  
Kitchen 

15267 
9956 
12948 
12828 

91 
60 

78 
77 

18-38-3 
16-26-3 
19-14-F 
16-38-3 

47 
40 
57 
40 

1% 

lU 

1% 

1% 

1% 
114 

Reception  H.__ 
Chamber  1  ___ 
Chamber  2  
Chamber  3  
Chamber  4  _._ 
Bath  

14059 
10583 
11770 
9092 
8892 
5179 

84 
63 
71 
55 
53 
31 

17-38-3 
17-26-3 
19-26-3 
15-26-3 
15-26-3 
9-26-3 

42 
42 
57 
38 
38 
23 

1% 

1 
.1 
1 

% 

1% 

1 
1 
1 

% 

663 

188 


HEATING  AND   VENTILATION 


Fig.  101. 


HOT   WATER  AND   STEAM   HEATING  189 


Fig-.  102. 


190 


HEATING  AND   VENTILATION 


SECOND  FLOOR  PLAN 

CEILING     9' 

t 


Fig.  103. 


HOT   WATER   AND   STEAM  HEATING  191 


MAIN  AND  RISER  LAYOUT. 

Pig.  104. 

111.  Insulating  Steam  P.ipes: — In  all  heating  systems, 
pipes  carrying  steam  or  water  should  be  insulated  to  reduce 
the  heat  losses  unless  these  pipes  are  to  serve  as  radiating 
surfaces.  In  most  plants  the  heat  lost  through  these  unpro- 
tected surfaces,  if  saved,  would  soon  pay  for  first-class  in- 
sulation. The  heat  transmitted  to  ordinarily  still  air  through 
one  square  foot  of  the  average  horizontal  wrought  iron  pipe 
is  as  great  as  2.65  B.  t.  u.  per  hour,  per  degree  difference  of 
temperature  between  the  inside  and  the  outside  of  the  pipe. 


192  HEATIXC    AND    YKXTII.ATK  >X 

Assuming-  this  to  be  2.5,  with  steam  at  100  pounds  gage  and 
air  at  80°,  the  heat  loss  is  (338  —  80)  X  2.5  =  645  B.  t.  u.  per 
hour.  With  steam  at  50,  25  and  10  pounds  gage  respectively 
this  will  be  545,467  and  397  B.  t.  u.  .  If  the  pipes  were  located 
in  an  atmosphere  having  decided  air  currents  this  loss  would 
be  much  greater.  The  average  unprotected  low  pressure 
steam  pipe  will  probably  lose  between  350  and  400  B.  t.  u. 
per  square  foot  per  hour.  Assuming  this  to  be  375  and  ap- 
plying- it  to  a  6-inch  pipe  100  feet  in  length,  for  a  period  of 
240  days  at  20  hours  a  day,  we  have  a  heat  loss  of  171  X 
375  X  240  X  20  =  307800000  B.  t.  u.  With  coal  at  13000  B.  t. 
u.  per  pound  and  a  furnace  efficiency  of  60  per  cent,  this  will 
be  equivalent  to  39461  pounds  of  coal,  which  at  $3.50  per  ton 
will  amount  to  $69.05.  From  tests  that  have  been  run  on  the 
best  grades  of  pipe  insulation,  it  is  shown  that  80  to  85  per 
cent,  of  this  heat  loss  may  be  saved.  Taking  the  lower  value 
there  would  be  a  financial  saving  of  $55.24  if  covering  were 
used.  If  a  good  grade  of  pipe  covering  installed  on  the  pipe 
is  worth  $85.00  the  saving  in  one  and  one-half  year's  time 
would  nearly  pay  for  the  covering. 

To  be  effective,  insulation  should  be  cellular  but  should 
not  permit  air  circulation.  Small  voids  filled  with  still  air 
are  among  the  best  insulators,  consequently  hair  felt,  min- 
eral wool,  eiderdown  and  other  loosely  woven  materials  are 
very  efficient.  Some  insulating  materials  disintegrate  after 
a  time  and  lose  their  form  but  many  patented  coverings  have 
good  insulating  qualities  as  well  as  permanency.  Most 
patented  coverings  are  1  inch  in  thickness  and  may  or  may 
not  fit  closely  to  the  pipe.  A  good  arrangement  is  to  select 
a  covering  one  size  larger  than  the  pipe  and  set  this  off  from 
the  pipe  by  spacer  rings.  The  air  space  between  the  pipe  and 
the  patented  covering  renders  the  covering  more  efficient. 
Table  50,  Appendix,  gives  the  results  of  a  series  of  experi- 
ments on  pipe  covering,  obtained  at  Cornell  University  under 
the  direction  of  Professor  Carpenter. 

112.  Water  Hammer: — When  steam  is  admitted  to  a 
pipe?  that  is  full  of  water,  it  is  suddenly  condensed  causing 
a  sharp  cracking  noise.  The  concussion  produced  may  be- 
come so  severe  as  to  crack  the  fittings  or  open  up  the  joints. 
The  noise  is  due  to  the  sudden  rush  of  water  from  the  sur- 
rounding space  in  an  endeavor  to  fill  the  vacuum  produced 
by  the  condensed  steam.  Steam  at  atmospheric  pressure 


HOT  WATER   AND    STTCAM  HEATING  193 

occupies  1650  times  the  volume  of  the  water  that  formed  it, 
so  when  this  steam  is  suddenly  condensed  a  very  high  vac- 
uum is  produced  which  caused  a  relatively  high  velocity  in 
the  water  adjacent  to  it.  Steam  should  always  be  admitted 
very  slowly  to  a  cold  pipe  or  to  one  filled  with  water. 

Water  hammer  is  frequently  produced  in  water  mains 
by  suddenly  stopping-  the  stream  of  flowing  water.  For  a 
theoretical  discussion  of  this  subject  see  Church's  Hydraulic 
Motors,  page  203.  To  find  the  approximate  pressure  p  in 
pounds  per  square  inch,  produced  by  water  hammer  when 
v  =  velocity  of  the  water  in  feet  per  second,  use  p  =  63  r. 
Also,  to  find  the  least  time  in  seconds  required  in  closing  a 
valve  on  a  water  main  that  water  hammer  may  be  avoided, 
divide  twice  the  length  of  the  pipe  stream  by  4670  (See  ref- 
erence above).  To  illustrate.  Water  in  a  water  main  500 
feet  long  is  flowing  at  the  rate  of  10  feet  per  second.  If  the 
water  movement  "were  suddenly  stopped  by  closing  the  valve 
at  the  end  of  the  main  the  pressure  produced  at  the  valve 
would  be  approximately  630  pounds  per  square  inch.  The 
least  time  of  closing  the  valve  to  avoid  water  hammer  would 
be  1000  -f-  4670  =  .21  second. 

113.  Returning  the  Water  of  Condensation  from  a  Low 
Pressure  Steam  Heating  System  to  the  Boiler: — In  returning 
the  water  of  condensation  to  a  boiler  four  methods  are  in 
use;  gravity,  steam  traps,  steam  loops  and  steam  or  electrxc 
pumps.  The  gravity  system  is  the  simplest  and  is  used  in  all 
cases  where  the  radiation  is  above  the  level  of  the  boiler 
and  where  the  boiler  pressure  is  used  in  the  mains.  In  a 
gravity  return  no  special  valves  or  fittings  are  necessary 
but  a  free  path  with  the  least  amount  of  friction  in  it  is 
provided  between  the  radiators  and  some  point  on  the  boiler 
below  the  water  line.  No  traps  of  any  kind  should  be  placed 
in  this  return  circuit. 

All  radiation  should  be  placed  at  least  18  inches  above 
the  water  line  of  the  boiler  to  insure  that  the  water  will  not 
back  up  in  the  return  line  and  flood  the  lower  radiators. 
Flooding  usually  takes  place  through  the  return  main  and 
is  the  result  of  a  restricted  steam  main.  It  may  be  due  to 
a  boiler  which  is  too  small  and  has  to  be  forced  thus  caus- 
ing siphonage.  Where  the  radiation  is  below  the  water  line, 
or  where  the  pressure  in  the  mains  is  less  than  that  in  the 
boiler,  some  form  of  steam  trap  or  motor  pump  must  be  put 


194 


HEATING  AND   VENTILATION 


in  with  special  provision  for  returning-  the  water  of  conden- 
sation to  the  boiler.  Two  kinds  of  traps  may  be  had,  low 
pressure  and  high  pressure.  The  first  is  well  represented  by 
the  bucket  trap,  Fig.  105,  and  the  second  by  the  Bundy  trap, 
Fig.  106.  The  action  of  these  traps  is  as  follows:  Bucket 
trap. — Water  enters  at  D  and  collects  around  the  bucket 


Fig.  105. 


Fig-.  106. 


which  is  buoyed  up  against  the  valve.  Water  fills  in  and 
overflows  the  bucket  until  the  combined  weight  of  the  water 
and  bucket  overbalances  the  buoyancy  of  the  water.  The 
bucket  then  drops  and  the  steam  pressure  upon  the  inside, 
acting  upon  the  surface  of  the  water,  forces  it  out  through 
the  valve  and  central  stem  to  outlet  B.  When  a  certain 
amount  of  water  has  been  ejected  the  bucket  again  rises  and 
closes  the  valve.  This  action  is  continuous.  Bundy  trap. — 
Water  enters  at  D  through  the  central  stem  and  collects  in 
bowl  A  which  is  held  in  its  upper  position  by  a  balanced 
weight.  When  the  water  collects  in  the  bowl  sufficiently  to 
lift  the  weight,  the  bowl  drops,  valve  E  opens,  and  steam  is 
admitted  to  the  bowl  thus  forcing  the  water  out  through  the 
curved  pipe  and  valve  E.  This  action  is  continuous. 

Each  trap  is  capable  of  lifting  the  water  2.4  feet  above 
the  trap  for  each  pound  of  differential  pressure.  Thus,  for 
a  pressure  of  5  pounds  gage  within  the  boiler  and  2  pounds 
gage  on  the  return,  the  water  may  be  lifted  7  feet  above  the 
trap,  or  to  the  top  of  an  ordinary  boiler.  This  is  not  suffi- 
cient, however,  to  admit  the  water  into  the  boiler  against 
the  pressure  of  the  steam.  A  receiver  should  be  placed  here 
to  catch  the  water  from  the  separating  trap  and  deliver  it  to 
a  second  trap  above  the  boiler,  which  in  turn  feeds  the 
boiler.  Live  steam  is  piped  from  the  boiler  to  each  trap,  but 
the  steam  supply  to  the  lower  trap  is  throttled  to  give  only 
enough  pressure  to  lift  the  water  into  the  receiver.  A  sys- 


HOT  WATER  AND   STEAM   HEATING 


195 


tem  connected  in  this  way  is  shown  in  Fig.  107.  Here  the 
receiver  and  trap  are  combined.  Traps  which  receive  the 
water  of  condensation  for  the  purpose  of  feeding-  the  boiler 
are  called  return  traps  and  sometimes  work  under  a  higher 

pressure  of  steam  than  the 
separating  traps.  Many  dif- 
ferent kinds  of  traps  are  in 
general  use  but  these  will 
illustrate  the  principle  of 
operation. 

A  very  simple  arrangement 
and  a  very  difficult  one  to 
operate  satisfactorily,  is  the 
steam  loop  (Fig.  108).  The 
water  of  condensation  from 
the  radiators  drains  to  re- 
ceiver A,  which  is  in  direct 
communication  with  riser  B. 
Drop  leg  D,  being  in  com- 

VENTPtft  TO  ASH  PIT 

munication    with    the    boiler 

Fig.  107.  through  a  check  valve  which 

opens  toward  the  boiler  at  the  lowest  point,  is  filled 
with  water  to  point  X  sufficiently  high  above  the  water 


A 

&005E  NECK 

IR  VALVE 

A 

CONDENSER     C      | 

r~ 

0 

* 

Fig.  108. 


196  HEATING  AND   VENTILATION 

line  of  the  boiler  that  the  static  head  balances  the  differen- 
tial pressure  between  the  steam  in  the  boiler  and  that  in  the 
condenser.  Horizontal  pipe  C  serves  as  a  condenser  which 
produces  a  partial  vacuum  and  lifts  the  water  from  the  re- 
ceiver. This  water  is  not  raised  as  a  solid  body,  but  as  slugs 
of  water  interspersed  with  quantities  of  steam  and  vapor. 
The  water  in  A  is  at  or  near  the  boiling  point  and  the  re- 
duced pressure  in  B  re-evaporates  a  portion  of  it  which,  in 
rising  as  a  vapor,  assists  in  carrying  the  rest  of  the  water 
over  the  gooseneck.  When  the  condensation  in  D  rises  above 
point  A',  the  static  pressure  overbalances  the  differential 
steam  pressure,  and  water  is  fed  to  the  boiler  through  the 
check. 

To  find  the  location  of  point  A"  above  the  water  line  in 
the  boiler,  the  following  will  illustrate.  Let  the  pressure  in 
the  boiler,  condenser  and  receiver  be  respectively  5,  2  and  4 
pounds  gage;  then  the  differential  pressure  between  the 
boiler  and  condenser  is  3  pounds  per  square  inch.  If  the 
weight  of  one  cubic  foot  of  water  at  212°  is  59.76  pounds,  the 
pressure  is  .42  pound  per  square  inch  for  each  foot  in  height, 
i.  e.,  one  pound  differential  pressure  will  sustain  2.4  feet  of 
water.  With  a  press.ure  difference  of  3  pounds  this  gives 
3  4-  .42  =  7.2  feet  from  the  water  level  in  the  boiler  to  point 
A',  not  taking  into  account  the  friction  of  the  piping  and 
check  which  would  vary  from  10  to  30  per  cent.  Assuming 
the  friction  to  be  20  per  cent,  we  have  the  static  head  r= 
7.2  -f-  .80  =:  9  feet  to  produce  motion  of  the  water  toward  the 
boiler. 

The  length  of  riser  pipe  B  and  its  diameter  depends  upon  the 
differential  pressure  between  the  condenser  and  the  receiver, 
and  upon  the  rapidity  of  condensation  in  the  horizontal.  A 
differential  pressure  of  2  pounds  will  suspend  2  X  2.4  =  4.8 
feet  of  solid  water,  but  the  specific  gravity  of  the  mixture  in 
this  pipe  is  much  less  than  that  of  solid  water.  For  the  sake 
of  argument  let  it  be  20  per  cent,  of  that  of  solid  water,  in 
which  case  we  would  have  a  possible  lift,  not  including  fric- 
tion, of  5  X  4.8  =:  24  feet.  This  is  24  —  9  —  15  feet  below 
the  water  level  in  the  boiler.  The  diameter  of  the  riser  may 
vary  for  different  plants,  but  for  any  given  plant  the  range 
of  diameters  is  very  limited.  These  are  found  by  experiment. 


HOT  WATER  AND   STEAM   HEATING 


197 


A  drain  cock  should  be  placed  in  the  receiver  at  the 
lowest  point.  When  cold  water  has  collected  in  the  receiver 
it  is  necessary  to  drain  this  water  to  the  sewer  before  the 
loop  will  work.  An  air  valve  should  be  placed  at  the  top  of 
the  g-ooseneck  to  draw  off  the  air.  If  the  horizontal  pipe  is 
filled  with  air,  there  will  be  no  condensation  and  the  loop 
will  refuse  to  work.  Never  connect  a  steam  loop  to  a  boiler 
in  connection  with  a  pump  or  any  other  boiler  feeder.  To 
determine  whether  a  loop  is  working  place  the  hand  on  the 
horizontal  pipe.  If  this  is  cold  it  is  not  working. 

The  steam  loop  is  used  with  success  in  factories  and 
manufacturing-  plants  in  returning  steam  separator  drips  to 
boilers.  In  a  series  of  experiments  conducted  in  1910,  the 
condensation  from  four  100  square  foot  radiators  was  lifted 
21  feet  to  a  coil  condenser  and  delivered  by  gravity  to  a 


Fig.  109. 


pressure  tank  located  5  feet  above  the  receiver  and  main- 
tained at  a  pressure  l1/^  pounds  above  the  receiver  pressure. 
Much  experimentation  will  be  necessary  before  the  riser 
diameters  and  the  condenser  surfaces  will  be  properly  pro- 
portioned to  be  of  general  usefulness  in  heating  systems. 
The  last  method  mentioned  for  feeding  condensation  to 
the  boiler  was  a  steam  or  electric  pump.  The  operation  of  the 
steam  pump  is  fully  discussed  in  Art.  186.  An  electric  motor- 
pump  with  its  receiver  and  pipe  connections  is  shown  in  Fig. 
109.  Its  operation  is  very  similar  to  that  of  the  steam  pump. 


198 


HEATING  AND  VENTILATION 


When  the  returning  condensation  fills  the  receiver  to  a  cer- 
tain level  a  float  regulator  starts  the  motor  and  pumps  the 
water  from  the  receiver  to  the  boiler.  When  the  water  level 
drops  the  operation  is  reversed  and  the  pump  is  automat- 
ically stopped.  The  motor  pump  is  used  on  low  pressure 
heating  systems  where  the  water  of  condensation  from  the 
coils  and  radiators  drains  below  the  boiler.  If  the  boiler 
pressure  were  high  the  ordinary  steam  pump  would  be  pre- 
ferred. Where  the  pressure  within  the  boiler  is  near  that  in 
the  return  main  the  operation  of  such  a  piece  of  apparatus 
is  less  expensive  than  that  of  the  steam  pump. 

114.  Hot  "Water  Heating  for  Tanks  and  Pools: — The  de- 
termination of  the  amount  of  heat  transmitted,  the  amount 
of  water  heated  and  the  square  feet  of  coil  surface  needed 
for  heating  water  by  the  use  of  immersed  steam  coils,  fol- 
lows closely  the  work  given  under  hot  water  heating,  Art. 
101,  Equations  49  and  50.  From  experiments  conducted  by  the 
American  Radiator  Co.,  at  the  Institute  of  Thermal  Research, 
the  amount  of  heat  transmitted  in  B.  t.  u.  per  hour,  K  [ts  — 
(ta  +  U)  -f-  2],  through  iron  and  brass  pipes  from,  steam 
(up  to  10  Ibs.  gage)  to  water,  allowing  an  efficiency  of  50 
per  cent,  for  fouling  of  the  pipes  is: 


Dif  f.  between  steam  temp,  and 
av.  temp,  of  water, 
degrees 

50 

70 

100 

150 

200 

Brass  _  _  

7200 

12800 

24000 

48000 

80000 

Iron  .  __ 

4500 

8000 

15000 

30000 

50000 

Knowing  the  amount  of  water  to  be  heated  through  a 
given  temperature  difference,  the  coil  surface  and  the  steam 
condensed  may  be  determined. 

APPLICATION. — Required  to  heat  3000  pounds  of  water  per 
hour  from  60°  to  90°  with  steam  at  5  Ibs.  gage  pressure. 
How  many  pounds  of  steam  will  be  condensed  per  hour  and 
how  many  square  feet  of  iron  coil  surface  will  be  necessary. 

Result. — Steam  temperature,  227°;  average  temperature 
of  water,  75°;  temperature  difference,  152  degrees;  heat  given 
to  water,  90000  B.  t.  u.;  steam  condensed,  92.2  Ibs.;  coil  sur- 
face, 3  square  feet. 


HOT  WATER  AND   STEAM  HEATING  199 

115.  Suggestions  for  Operating  Hot  Water  Heaters  and 
Steam  Boilers: — Before  firing  up  in  the  morning-  examine  the 
pressure  gage  to  see  if  the  system  is  full  of  water.  If  there 
is  any  doubt,  inspect  the  water  level  in  the  expansion  tank. 
If  it  is  a  steam  system,  examine  the  gage  glass  and  try  the 
cocks  to  see  if  there  is  sufficient  water  in  the  boiler. 

See  that  all  valves  on  the  water  lines  are  open.  On  the 
steam  system  try  the  safety  valve  to  make  sure  that  it  is 
free.  Also  see  if  the  pressure  gage  stands  at  zero. 

In  starting  a  fire  under  a  cold  boiler  it  should  not  be 
forced  but  should  warm  up  gradually. 

For  suggestions  on   firing  read  Art.   77. 

In  a  boiler  or  heater  using  the  same  water  continuously 
(the  best  plan)  there  will  be  little  need  of  cleaning  the  in- 
side of  the  boiler.  Where  fresh  water  is  used  frequently 
soft  water  should  be  used.  Where  hard  water  is  used  the 
boiler  should  be  blown  off  and  cleaned  once  or  twice  a  month. 

Never  blow  off  a  boiler  while  hot  or  under  heavy  pres- 
sure. 

Inspect  the  pressure  gage,  glass  gage,  water  cocks  and 
thermometers  frequently. 

In  case  of  high  steam  pressure  in  a  steam  system,  cover 
the  fire  with  wet  ashes  or  coal  and  close  all  the  drafts.  Do 
not  open  the  safety  valve.  Do  not  feed  water  to  the  boiler. 
Do  not  draw  the  fire.  Keep  the  conditions  such  as  to  avoid 
any  sudden  shock.  After  the  steam  pressure  has  dropped 
sufficiently  examine  the  safety  valve. 

Excessive  pressure  may  be  caused  by  the  sticking  of  the 
safety  valve  in  the  steam  system,  or  by  the  stoppage  of  the 
water  line  to  the  expansion  tank  in  the  hot  water  system. 
The  safety  valve  should  never  be  allowed  to  lime  up,  and  the 
expansion  tank  should  always  be  open  to  the  heater  and  to 
the  overflow. 

In  case  of  low  water  in  a  steam  system,  cool  the  fire, 
lower  the  pressure  to  atmosphere  and  fill  the  boiler. 

When  leaving  the  fire  for  the  night  shake  down  and 
bank  as  stated  in  Art.  77. 


CHAPTER  IX. 


MECHANICAL    VACUUM    HEATING    SYSTEMS. 


116.  Return  Line  Systems. — Air  and  Condensate  Com- 
bined:— The  term  "vacuum  heating"  may  properly  be  ap- 
plied to  that  class  of  heating  systems  having  a  continuous 
negative  pressure  within  the  return  main,  the  pressure 
within  the  radiators  being  controlled  by  the  interposition 
of  some  form  of  thermal  or  float  valve  between  the  return 
main  and  the  radiators.  The  vacuum  may  be  produced  by 
pumps  or  ejectors.  In  point  of  design  this  is  the  extreme 
in  its  departure  from  the  low  pressure  gravity  system  and 
has  the  following  advantages  over  it: 

1.  A   positive    and    rapid    return    of    the    water    of    con- 
densation. 

2.  In   case   of  improper  alignment   of  main  and   return 
pipes   the   negative    effect   of   water   and    air   pockets    is    re- 
duced to  a  minimum. 

3.  Radiation    at    low    levels    may    be    drained    by    main- 
taining a  vacuum  in  the  return  line  proportional  to  the  lift 
of  the  water  of  condensation. 

4.  Smaller  return  pipes  may  be  used  than  are  used  on 
the  ordinary  gravity  systems. 

5.  A  continuous  withdrawal  of  the   entrained  air  from 
the  radiators  with  the  water  of  condensation.     This  insures 
a  high  efficiency  of  all  the  heating  surface.     This  statement 
may  not  hold  good  for  high  radiators  (36  to  48  inch)   on  the 
extreme  end  of  a  long  heat  run.     On  such  radiators,  air  valves 
may  be  necessary. 

6.  This  system  is  especially  adapted  to   the  use   of  ex- 
haust steam  with  its  extra  large  air  and  water  content. 

7.  Comparative  freedom  from  pounding  and  water  ham- 
mer. 

On  the  other  hand  there  is  an  additional  cost  in  main- 
taining the  vacuum,  and  its  use  is  restricted  in  small  plants 
because  of  the  extra  cost  of  installation  and  superintendence. 

Mechanical  Vacuum  systems  of  heating  are  frequently  in- 
stalled in  connection  with  lighting  or  power  units  in  which 


MECHANICAL  VACUUM  HEATING 


201 


case  the  exhaust  steam  may  be  used  to  supplement  the  live 
steam  for  heating.  This  substitution  results  in  a  great 
economy  for  the  plant.  A  diagrammatic  view  showing 
the  principal  apparatus  involved  in  such  a  plant  is  shown 
in  Fig.  110.  Live  steam  is  connected  to  the  power  units  and 
to  the  heating  main,  the  latter  through  a  pressure  reducing 
valve  to  be  used  only  when  exhaust  steam  is  insufficient. 


UHCUUM   VALVCS  - 


I - JPETURN.  MAJN. I 


Fig.  110. 

Exhaust  steam  from  the  power  units  is  connected  to  the 
heating  main  and  to  the  feed  water  heater.  This  exhaust 
steam  line  opens  to  the  atmosphere  through  a  back  pres- 
sure valve  which  is  set  at  the  desired  pressure  for  the  sup- 
ply steam.  Oil  separators  remove  the  oil  from  the  exhaust 
steam  and  deliver  it  to  the  oil  traps.  Boiler  feed  pumps 
and  vacuum  pumps,  with  the  accompanying  valves  and 
governing  appliances,  complete  the  essentials  of  the  power 
room  equipment. 

The  steam  supply  to  the  heating  system  is  piped  to 
radiators  and  coils  in  the  ordinary  way,  with  or  without 
temperature  control.  Thermostatic  valves,  or  equivalent, 
are  placed  at  the  return  end  of  each  radiator  and  coil,  and 
the  returns  from  these  are  brought  together  in  a  common 
return  which  leads  to  the  vacuum  pump  or  ejector.  The  size 
of  the  return  pipe  and  specialty  valve  for  any  one  unit  is 


202 


HEATING  AND  VENTILATION 


usually  ^-inch,  increasing  in  size  as  more  radiating  units 
are  taken  on.  Horizontal  steam  mains  usually  terminate  in 
a  drop  leg  which  is  tapped  to  the  return  8  to  15  inches  above 
the  bottom  of  the  leg.  Each  rise  in  the  system  has  a  drop 
leg  at  the  lower  end  of  the  rise.  These  points  and  all  others 
where  condensation  and  dirt  may  collect  are  drained  through 
special  separator  valves  to  the  return.  Steam  is  carried  in 
the  main  slightly  above  atmospheric  pressure  and  just 
enough  vacuum  is  maintained  on  the  return  to  insure  posi- 
tive and  noiseless  circulation.  In  many  cases  where  special 
lifts  are  required,  these  return  systems  are  run  under  pres- 
sures 6  to  10  inches  of  mercury  below  atmospheric  pressure. 
Under  such  conditions  water  may  be  lifted  from  6  to  10  feet. 
Either  closed  or  open  feed  water  heaters  may  be  used. 

When  water  of  condensation  at  212°  or  above  is  re- 
leased from  the  radiator  through  the  vacuum  valve  to  the 
returns  with  pressure  below  atmosphere,  the  result  is  a  very 


EXHAUST  TO  ATM05PHECC 


PBE55UBE  REDUCING 

VALVE; 

3TEAM 

EXHAUST  5TE#1     5EPACATOC 
TO  HEATING 


Fig.  111. 

quick  withdrawal  and  a  partial  re-evaporation  of  the  water 
into  steam  or  vapor  at  the  lower  pressure.  If  large  amounts 
of  condensation  were  thus  released  at  one  time,  the  vacuum 
would  be  temporarily  broken,  but  being  divided  into  a  large 
number  of  small  units  having  no  regularity  in  the  time  of 
action,  there  is  little  difficulty.  Although  the  vacuum  is 
supposed  to  extend  only  from  the  pump  to  the  vacuum  valve, 
it  may  extend  to  within  the  radiator  if  the  vacuum  valve  is 
set  for  a  constant  discharge.  Such  an  arrangement  cannot 


MECHANICAL  VACUUM   HEATING  203 

be  justified  from  the  standpoint  of  economy,  singe  the  latent 
heat  of  all  the  leakage  steam  is  lost  from  the  heating  system 
and  thrown  away.  Just  before  entering  the  vacuum  pump, 
the  steam  and  water  vapor  mixed  with  the  return  water 
may  be  condensed  by  a  spray  of  cold  water.  This  spray 
assists  in  increasing  the  vacuum.  From  the  vacuum  pump 
the  returns  go  to  a  feed  water  heater  (open  or  closed)  and 
from  this  by  a  boiler  feed  pump  back  to  the  boiler.  The 
Webster  system,  shown  in  detail  in  Fig.  Ill,  is  a  typical  repre- 
sentative of  this  class.  In  all  essential  features  this  figure 
may  stand  for  a  number  of  others,  among  them  the  Dunham, 
the  Bishop  and  Babcock,  the  Illinois  and  the  Automatic.  For 
comparative  sizes  of  gravity  and  mechanical  vacuum  return 
pipes  see  Table  43,  Appendix. 

117.  Air  Line  Systems. — Air  and  Condensate  Separate: — 
Representing  this  type  of  heating  is  the  so-called  Paul 
system.  It  is  usually  installed  as  a  one-pipe  system,  fed 
from  overhead  supply  and  drained  to  a  wet  return,  although 
it  may  be  connected  up  as  a  two-pipe  system  or  fed  from 
a  basement  supply.  The  air  pump  handles  the  water  of  con- 
densation but  is  not  installed  as  a  vacuum  producing  agent. 
The  vacuum  in  the  air  line  connecting  with  the  air  valves 
at  the  radiators,  is  produced  by  a  steam,  air  or  hydraulic 
ejector  which  discharges  directly  into  the  atmosphere,  into 
the  atmospheric  end  of  the  exhaust  heating  main  or  into  a 
secondary  radiator  where  a  separation  is  made,  the  water 
dropping  to  a  receiver  to  be  further  used  and  the  air  ex- 
hausting to  the  atmosphere.  This  system  differs  from  the 
ones  mentioned  in  two  essential  points;  first,  the  vacuum 
effect  is  applied  at  the  air  valve  and  the  flow  of  water  of 
condensation  is  independent  of  the  vacuum;  second,  the 
vacuum  effect  is  produced  by  the  aspirator  principle  using 
water,  steam  or  compressed  air  as  motive  power.  The 
vacuum  is  supposed  to  extend  only  to  the  air  valve  at  the 
radiator,  but  if  desired  this  valve  may  be  adjusted  so  that 
the  vacuum  may  have  an  effect  within  the  radiator.  The 
layout  of  the  system  for  large  plants  is  about  that  shown 
in  Fig.  112.  This  system  is  especially  adapted  to  small 
plants  having  one-pipe  complete  circuit  mains,  because  of 
its  effectiveness  in  removing  air  from  one-pipe  radiators. 
When  thus  used  the  pump  is  omitted  and  the  cohdensate 
flows  direct  to  the  boiler  by  the  one-pipe  gravity  method. 


204 


HEATING  AND  VENTILATION 


Fig.  112. 

Fig".  113  shows  typical  vacuum  connections  between  one-pipe 
and   two-pipe   radiators  and   the   exhauster.     Where   electric 


MECHANICAL  VACUUM   HEATING  205 

current   is   available  exhausting  may   be  done   by   the   use   of 
an  electric  motor  pump. 

118.  Vacuum  Pumps: — The  satisfactory  operation  of 
vacuum  heating  systems  depends  upon  the  effective  removal 
of  air  and  water  from  the  system.  Reciprocating  pumps 
(modified  types  of  the  direct  acting  piston  pump)  are  gen- 
erally used  in  producing  the  vacuum.  Fig'.  114  is  a  sec- 
tional view  of  the  valve  governing  the  action  of  the  Ameri- 


Tr/p  Fbrt 


Sec  f ion  atffB 
/Exhaust  P/pe 
Fig.  114. 

can-Marsh  Vacuum  Pump.  Steam  enters  the  chest  through 
the  pipe  at  K  and  a  small  amount  passes  through  the  port 
C  to  the  auxiliary  Valve  D.  Auxiliary  Valve  D  is  operated 
by  a  lever  connected  to  the  crosshead  on  the  piston  rod,  and 
can  be  regulated  by  two  adjusting  screws.  When  the  piston 
reaches  the  end  of  its  stroke,  steam  is  admitted  by  auxiliary 
valve  through  the  small  port  X  outside  of  the  rear  head  of 
the  main  valve,  forcing  it  forward  to  the  position  shown 
in  the  figure.  When  in  this  position  steam  travels  through 
the  steam  port  E  and  moves  the  piston  to  the  opposite  end 
of  its  stroke,  the  pump  exhausting  through  the  passage  F 
as  shown  by  arrows.  Exhaust  from  the  opposite  end  of  the 
valve  escapes  through  port  X'  and  valve  7)  to  the  main  ex- 
haust pipe.  To  hold  the  main  valve  in  position  after  the 
auxiliary  has  placed  it,  live  steam  is  admitted  through  bal- 
ancing port  G  maintaining  high  pressure  against  the  outside 
of  the  head,  which  more  than  balances  the  pressure  on  the 
inside  of  this  same  head  owing  to  the  difference  of  .the  area 
on  either  side.  Port  Y  at  each  end  of  the  valve  prevents  the 
valve  from  centering.  In  any  position  of  the  valve  one  of 
these  ports  is  open  to  steam  pressure  and  conducts  steam 
to  the  outside  of  the  valve  head  causing  the  valve  to  move 
into  operating  position.  When  the  piston  reaches  the  for- 
ward end  of  its  stroke  the  operation  is  repeated  at  the  for- 


206 


HEATING   AND   VENTILATION 


ward  end  of  the  valve.  A  few  of  the  sizes  and  capacities  of 
these  pumps  for  the  average  mechanical  vacuum  heating- 
system  are  given  in  Table  XXI. 

TABLE  XXI. 
Capacities  of  Marsh  Vacuum  Pumps. 


Steam  pressure  5  to  10  Ibs. 

Steam  pressure  50  Ibs.  and  above 

Not  over  2  Ibs.  back  pressure. 

For  discharging1  into  open  receiver 

Size,  inches 

Sq.  ft.  direct  rad. 

Size,  inches 

Sq.  ft.  direct  rad. 

4x3x6 

1200 

7x3x8 

1250 

4x4x6 

2200 

8x3V2x8 

1800 

4x5x6 

3400 

10x4x12 

4000 

4x5x8 

4500 

12x5x12 

6500 

5x6x10 

8000 

14x6x12 

8500 

5x7%xlO 

'       12000 

16x7^x12 

12000 

6x8x12 

18000 

16x8x12 

15000 

8x10x12 

30000 

18x9x12 

20000 

Two  systems  of  regulation  are  in  common  use  in  connection 
with  piston  vacuum  pumps.  In  Fig.  115  the  pressure  in  the 
return  operates  through  the  governor  to  regulate  the  supply 
of  steam  to  the  pump,  thus  controlling  its  speed.  In  Fig. 
116  the  pressure  in  the  return  controls  the  flow  of  injection 


VACUUM     PUMP' 

Fig.  115 


Fig.  116 


water  into  the  suction  strainer  and  hence  the  rapidity  of 
vapor  condensation  in  the  return.  Either  system  provides 
automatic  control  for  the  vacuum.  Injection  water  for  the 
production  of  vacuum  is  not  a  necessity  in  vacuum  returns. 
Systems  are  operating  satisfactorily  without  it. 

Occasionally  it  is  desirable  to  have  the  returns  for  certain 
parts  of  heating   systems   under  different  nicuuin.     As   an   illus- 


MECHANICAL  VACUUM  HEATING 


207 


tration  of  this,  suppose  the  returns  for  the  radiators  within 
a  building;  are  expected  to  carry  condensate  at  atmospheric 
pressure  and  the  returns  from  a  set  of  heating-  coils  in  the 
basement  condensate  at  four  pounds  below  atmosphere.  This 
may  be  accomplished  by  placing-  a  pressure  regulating-  valve 
in  the  branch  requiring  the  least  negative  pressure  (the 
higher  line),  as  shown  by  Type  D  connection  in  the  Web- 


CONNECT   INTO 

TOP  or  RETURN 
Fig.  117.  Fig.  118. 

ester  system,  Fig.  117.  The  differential  pressure  between  the 
atmospheric  and  vacuum  lines  may  be  varied  to  suit  any 
condition  by  the  controller  valve.  A  trap  and  a  controller 
valve  are  applied  to  each  line  having  a  different  pressure 
from  that  in  the  main  suction  line. 

Strainers  or  dirt  catchers  are  installed  next  the  pump  on 
mechanical  vacuum  returns,  to  protect  it  from  the  cutting 
action  of  the  core  sand  and  dirt  from  the  radiators.  Where 
large  amounts  of  radiation  are  grouped,  a  dirt  catcher  may 
be  placed  at  the  outlet  of  each  group.  (See  Figs.  115,  116 
and  118). 


Fig.  119, 


208 


HEATING  AND   VENTILATION 


Centrifugal  pumps  are  being  increasingly  used  on  vacuum 
returns  where  a  moderate  vacuum  only  is  to  be  maintained. 
The  Nash  Hydroturbine  (Fig.  119)  represents  this  class. 
The  pump  consists  of  independent  water  and  air  units 
mounted  on  the  same  shaft.  The  water  end  is  the  usual 
centrifugal  pump.  The  air  and  vapor  pump  (transverse  sec- 
tion) shows  a  water  wheel  rotating  in  an  elliptical  casing 
partly  filled  with  water.  The  water  as  it  follows  the  wheel 
also  follows  the  contour-of  the  casing,  this  alternately  mov- 
ing from  and  toward  the  shaft  and  thus  drawing  in  and 
exhausting  continuously  and  without  pulsation.  In  opera- 
•  tion  the  centrifugal  pump  handles  water  in  coming  up  to 
speed  and  continues  automatic  operation  when  there  .  is  a 
water  supply.  The  air  pump  however  produces  continuous 
vacuum,  but  only  at  the  rated  speed.  Table  XXII  gives  rec- 
ommended sizes  and  capacities  of  this  pump. 


TABLE  XXII. 
Capacities  of  Nash  Vacuum  Pumps. 


Water 

Sq.  ft. 

Air 

capacity 

direct 

Diameter 

capacity 

gals. 

Actual 

H.  P. 

Size 

equivalent 

orifice 

cubic  ft. 

per  inin. 

Horse 

R.  P. 

of 

radiation 

inches 

per  mjn. 

lOlbs. 

Power 

M. 

Motor 

surface 

vac.  10  in. 

pres. 

180°  F. 

A 

8000 

9/64 

6 

11 

.9 

1800 

1 

B 

16000 

3/16 

11 

22 

1.4 

1808 

1% 

C 

26000 

1/4 

1!) 

35 

2  0 

1800 

9 

D 

40000 

9/32 

25 

60 

1200 

3 

E 

05000 

3/8 

42 

90 

3.9 

1200 

5 

119.  Vacuum  Specialties: — Classified  according  to  trade 
names  these  are: 

RETURN  WATER  LINES — radiator  traps,  thermo-traps,  vacu- 
traps,  sylphon  traps,  radifiers  and  water  seal  motors. 

AIR  LINES — vent  valves,  thermostatic  valves,  automatic 
expansion  valves  and  vacustats. 

Regardless  of  the  trade  names  and  the  locations  of  the 
fittings  on  the  systems,  they  may  be  classified  under  three 
heads: 

Type  A.  Thermostatic  valves — those  opening  and  clos- 
ing under  the  action  of  heat.  Automatic  and  adjustable. 


MECHANICAL  VACUUM  HEATING 


20U 


Type  B.  Float  valves — those  opening  and  closing1  under 
the  action  of  the  floatation  or  the  impulse  of  the  water  of 
condensation.  Automatic. 

Type  C.  Orifice — those  having-  a  constant  opening  and 
leakage.  Non-adjustable. 

Thcrmostatic  valves — Type  A.  Fig.  120  shows  modifications 
of  thermal  control.  The  Webster  composition  expansion  stem 
type,  one  of  the  earliest  forms  used  on  the  mechanical  vac- 
uum systems  is  still  used  on  many  installations.  The  auto- 


TRAME 


matic  feature  is  the  composition  rubber  stalk,  which  expands 
and  contracts  under  change  of  temperature.  The  adjusting 
screw  at  the  top  permits  the  valve  to  be  set  for  any  condi- 
tions of  temperature  and  pressure  within  the  radiator.  The 
water  of  condensation  passes  through  a  screen  and  comes  in 
contact  with  the  rubber  stalk.  The  temperature  of  the 
water  being  less  than  that  of  steam  the  stalk  contracts  and 
the  water  is  drawn  through  the  opening  A  by  the  action  of 


210 


HEATING  AND  VENTILATION 


the  pump.  As  soon  as  the  water  has  been  removed  steam 
flows  around  the  stalk  and  expands  it,  closing  the  port. 
This  process  is  continuous  and  automatically  removes  the 


DONNELLY 


MONA5H 


ILLINOIS 


WLB5TER 


Fig.  121. 


water  from  the  radiator.  The  screen  serves  as  a  dirt  catcher 
for  the  single  unit.  The  other  valves,  excepting  the  Trane, 
have  metal  expansion  chambers  partially  filled  with  liquids 


MECHANICAL   VACUUM   HEATING  211 

that  vaporize  at  temperatures  between  that  of  the  steam  and 
that  of  the  returning"  condensation.  In  most  cases  the  tem- 
perature approximates  200°  F.  The  change  in  the  vapor 
pressure  within  the  enclosed  chamber  causes  an  expansion 
or  contraction  of  the  sides  of  the  chamber  thus  closing  or 
opening  the  valve.  The  expansion  members  of  these  valves 
differ  in  form  and  position.  The  Dunham,  Monash  and  Illi- 
nois have  single  expansion  chambers,  the  sylphon  is  mul- 
tiple, or  accordion  form,  and  the  Haines  is  a  bent  tube. 
The  expansion  member  of  the  Trane  valve  is  composed  of 
two  sheet  metal  coil  springs  which  in  turn  are  made  of  two 
thin  pieces  of  dissimilar  metals  brazed  together.  Since  the 
coefficients  of  expansion  of  the  two  metals  are  unequal,  any 
change  of  heat  coils  or  uncoils  the  springs  thus  opening  or 
closing  the  valve.  Other  differences  in  these  valves  are  to 
be  found  in  the  construction  and  location  of  the  expansion 
member  and  in  the  style  and  location  of  the  valve  seat.  The 
expansion  member  of  four  of  the  valves  is  in  direct  connec- 
tion with  the  radiator  steam.  The  rest  are  in  connection 
with  the  return  line.  Two  of  the  valves  have  flat  seats, 
three  have  conical  seats  and  two  have  line  contact.  Four 
seats  are  horizontal  and  three  are  vertical.  Style  A  valves 
are  automatic,  positive,  noiseless  and  adjustable.  They  may 
be  used  under  either  high  or  low  differential  pressures  and 
may  be  used  on  either  air  or  condensation  lines. 

Float  valves — Type  B. — When  the  differential  pressure  be- 
tween the  radiator  and  the  return  is  very  small  and  a  fitting 
is  desired  that  will  serve  merely  as  a  separating  trap  to  the 
radiator,  a  float  valve  or  a  valve  actuated  by  the  impulse 
of  the  water  is  frequently  used.  Fig.  121  gives  five  of  the 
standard  forms.  There  are  five  important  features  consid- 
ered in  the  design  of  these  float  valves,  continuous  air  re- 
moval, intermittent  water  removal,  freedom  from  steam 
leakage,  convenience  in  cleaning  and  freedom  from  noise. 
This  is  a  combination  that  is  difficult  to  obtain.  The  first 
three  are  points  of  efficiency  and  are  not  easily  determined 
in  the  operation  of  the  average  plant  except  under  test. 
So  far  there  are  few  comparative  data  from  which  to  draw 
conclusions.  The  fourth  affects  the  attendant  who  has 
charge  of  the  repair  and  upkeep  of  the  plant,  and  the  fifth 
is  of  vital  interest  to  the  occupant  of  the  room.  One  of  the 
objections  frequently  offered  against  the  use  of  float  valves 


212  HEATING  AND   VENTILATION 

is  the  occasional  noisy  valve.  When  the  .differential  pres- 
sure between  the  radiator  and  the  return  is  so  small  that  it 
is  alternately  changing  positive  and  negative,  there  is  liable 
to  be  a  chattering1  of  the  valve,  which  is  very  annoying. 
This  is  not  general  but  frequently  obtains  in  one  or  more 
valves  in  a  system. 

Orifice — Type  C. — In  some  systems  the  return  fitting  takes 
the  form  of  a  standard  orifice  which  is  non-adjustable  and 
provides  constant  leakage.  The  use  of  such  fittings  is 
questionable. 

Concerning  the  economy  of  vacuum  licatiny  over  low  pres- 
sure heating,  many  claims  are  made,  some  of  which  would  be 
difficult  to  realize  in  practice.  Estimates  of  saving  range 
from  10  to  40  per  cent.  There  are  no  doubt  increased  econ- 
omies but  these  can  not  be  stated  in  percentages.  The  two 
features  of  such  a  system  that  give  decidedly  increased  effi- 
ciencies are  the  use  of  exhaust  steam  and  thermostatic  control  of 
the  steam  admitted  to  the  radiator,  but  each  of  these  may  be 
adapted  to  any  system  and  consequently  should  not  be  cred- 
ited here  as  economic  features.  On  the  other  hand  improve- 
ment in  operating  conditions  is  so  marked  that  a  general 
statement  of  higher  efficiencies  is  justifiable.  The  claim  is 
sometimes  made  that  a  mechanical  vacuum  system  using-  ex- 
haust steam  as  a  heating  medium  may  serve  as  a  condenser 
to  the  engine  and  improve  the  efficiency  of  the  engine  to  a 
marked  degree.  As  a  matter  of  fact  this  statement  will  sel- 
dom be  justified.  The  back  pressure  on  the  engine  "will  not 
drop  below  atmosphere  except  when  the  vacuum  return 
valves  are  given  a  constant  leakage,  in  which  case  there 
may  be  greater  loss  in  the  plant  from  the  latent  heat  of  the 
wasted  steam  than  gain  derived  from  the  increased  mean 
effective  pressure  in  the  engine.  The  one  larg-e  economy  to 
be  looked  for  in  heating  systems  lies  in  the  use  of  exhaust 
steam  as  the  heating  medium.  When  we  consider  the  fact 
that  exhaust  steam  at  atmospheric  pressure  contains  80  to  85 
per  cent,  of  the  total  heat  of  the  live  steam  entering  the 
cylinder  (Art.  164),  that  this  is  all  wasted  when  exhausted 
to  the  atmosphere,  that  the  condensing  engine  saves  only  a 
small  part  of  it  and  finally  that  the  heating  system  may 
save  it  all,  there  is  sufficient  reason  to  look  forward  to  its 
increased  use  in  combined  power  and  heating  plants. 


CHAPTER  X. 


MECHANICAL   WARM   AIR    HEATING   AND   VENTILATION 
FAN-COIL   SYSTEMS. 

DESCRIPTION  OF  SYSTEMS  AND  APPARATUS 
EMPLOYED. 

120.  Elements    of    the    Fan-Coil    System: — In    buildings 
having-    many    occupants    such    as    factories,    school    houses, 
theaters  and  auditoriums,  a  positive  air  supply  to  the  rooms 
is  usually  required.     To  meet  this  condition  there  has  "been 
developed   a    type    of   heating   and   ventilating   system    vari- 
ously known  as  the  fan-coil  system,  mechanical  warm  air  system 
or  plenum  system.     This  system  contemplates  the  use  of  three 
distinctly    vital    elements:    steam    or    hot    water    coils    over 
which   the  forced  air  may  pass  and  be  heated,   a  blower  or 
fan  to  propel  the  air  and  a  proper  system  of  ducts  or  pas- 
sageways  to  distribute  this  heated  air  to   the  desired  loca- 
tions.    Figs.  139  and  140  show  these  essentials  in  their  rela- 
tive positions.     Attachments  and  improved  mechanisms  such 
as  air  washers  and  humidifiers,  automatic  air  and  heat  con- 
trol systems  and  brine  cooling  systems  may  be  installed  in 
connection  with  this  type  of  heating  but  none  of  these  aux- 
iliaries change  in  any  way  the  necessity  for  the  three  funda- 
mentals named. 

121.  Variations    in    the    Design    of   Fan-Coil    Systems: — 

With  regard  to  the  position  of  the  fan,  two  methods  of  in- 
stallation are  common.  The  first  and  most  used  is  that 
shown  in  Fig.  122,  where  the  fan  is  in  the  basement  of  the 
building  and  forces  the  air  by  pressure  upward  through  the 
ducts  and  into  the  rooms.  This  arrangement  gives  the  air 
within  the  building  a  pressure  slightly  greater  than  that  of 
the  atmosphere,  causing  any  leakage  to  be  outward  from  the 
rooms.  A  system  so  installed  is  a  plenum  system.  The  fan 
may,  however,  be  placed  in  the  attic  (Fig.  123)  with  ducts 
leading  to  it  from  the  rooms,  in  which  case  the  air  is  pulled 
toward  the  fan  thus  causing  the  pressure  within  the  build- 
ing to  be  slightly  less  than  that  of  the  atmosphere.  In  the 
latter  case  the  air  is  supposed  to  enter  the  basement  inlet, 


214 


HEATING  AND   VENTILATION 


pass  over  the  coil  surfaces,  and  when  heated  pass  by  induc- 
tion to  the  various  rooms  through  the  ducts.  Since  the 
leakage  is  inward,  air  from  the  outside  readily  enters  at 
open  windows  and  doors,  breaking  the  vacuum  effect  of  the 
fan  and  by-passing  the  heater,  thus  impairing  the  efficiency 
of  the  heating  system.  For  this  reason  where  heating  is  a 
vital  factor,  exhaust  systems  without  the  aid  of  plenum  systems 
are  seldom  installed.  Combined  plenum  and  exhaust  systems 
are  to  be  recommended  wherever  the  expense  can  be  justified. 


/ 


Fig.  122. 


Fig.  123. 


122.  Blowers  and  Fans: — Many  methods  of  moving  air 
for  ventilating  and  heating  purposes  have  been  devised. 
Some  of  these  are  positive  at  all  times,  others  are  dependent 
upon  the  existence  of  constant  atmospheric  air  conditions 
and  hence  are  a  constant  source  of  trouble.  It  is  now  a  very 
generally  accepted  fact,  that  if  air  is  to  be  delivered  at 
definite  times,  in  definite  quantities  and  in  definite  places,  it 
must  be  forced  there  by  mechanical  means.  The  recognition 
of  this  fact  has  led  to  a  very  common  use  of  the  mechan- 
ical fan  or  blower  and  its  development  to  a  fairly  high 
efficiency. 


PLENUM  WARM  AIR  HEATING 


215 


Fig.  124. 

For  exhaust  service  the  fan  generally  used  is  of  the 
disk  or  propeller  blade  type  (Figs.  124  and  125).  It  is  usually 
installed  in  the  attic  or  near  the  top  of  the  building,  al- 


Fig.  125. 

though  in  certain  cases  where  the  plenum  fan  is  used  for 
exhaust  service  it  may  be  installed  in  the  basement.  The 
plenum  system  uses  a  centrifugal  fan  of  the  paddle  wheel  or 
the  multiple  blade  type  (Figs.  126  and  127).  The  first  with 


216 


HEATING   AND   VENTILATION 


plane  blades,  called  "steel  plate"  fan,  is  the  old  form  of  fan 
wheel  and  is  now  used  on  mechanical  draft  systems  in 
power  plants  and  on  the  cheaper  plenum  heating-  and  venti- 
lating- plants.  The  second  with  curved  blades,  called  "si- 
rocco," "multivane"  or  "conoidal"  fans  by  the  respective 
companies,  is  a  more  recent  development  and  is  especially 
adapted  to  plenum  plants.  Tests  of  the  multiple  blade  fans 
show  hig-her  efficiencies  than  are  possible  with  the  older 
forms.  In  the  plenum  systems  fans  are  placed  between  the 
air  intake  and  the  heater  coils  or  just  following  the  heater 
coils  (See  Art.  125).  For  theoretical  discussion  of  fans  and 
blowers  see  Trans.  A.  S.  H.  &  V.  E.,  Vol.  XXI,  p.  43;  Kent's 
M.  E.  Pocket-Book;  Marks'  M.  E.  Handbook;  and  Metal 
Worker,  May  2,  1908,  p.  44,  serial. 


Pig.  126. 


The  motive  power  for  fans  may  be  of  four  kinds:  elec- 
tric motor  or  steam  engine  (or  turbine),  either  direct  con- 
nected or  belted.  Which  one  of  these  drives  will  be  the  most 
appropriate  in  any  case  will  depend  entirely  upon  local  con- 
ditions and  the  nature  of  the  available  power  supply.  The 
steam  driven  engine  or  turbine  unit  is  the  most  economical 


PLENUM  WARM   AIR   HEATING 


217 


since  the  exhaust  steam  from  either  may  be  used  to  supple- 
ment the  live  steam  for  heating  (See  Arts  164  and  172). 
The  electric  drive  is  the  most  convenient  and  in  places  where 
fans  are  employed  for  cooling"  and  where  steam  is  carried 
at  pressures  too  low  to  operate  the  engines,  motor  drives 
should  be  installed.  Electric  motors  are  usually  belted  to 
the  fans.  This  permits  the  installation  of  motors  of  smaller 
sizes  and  higher  speeds  at  lower  initial  costs.  Most  of  the 
larger  engine  driven  units  are  direct-connected. 

Fan  housings  are  made  in  many  different  styles  and  of 
various  materials,  such  as  brick,  wood,  sheet  steel  or  com- 
binations of  these.  Steel  housings  are  the  most  common  and 
are  made  to  fit  any  requirement.  Full  housings  are  those  in 
which  the  entire  fan  wheel  is  encased  and  the  entire  unit  is 
above  the  floor  line.  TJircc-(in<irtcr  Jioitftitiyfi  are  those  in  which 
only  the  upper  three-fourths  of  the  fan  wheel  is  encased, 
the  completion  of  the  air-sweep  around  the  blades  being  ob- 
tained by  properly  forming  the  brick  foundation  upon  which 
the  fan  is  installed.  Large  fans  are  usually  three-quarter 
housed,  especially  if  they  are  to  deliver  air  into  underground 
ducts.  Fig.  128  shows  a  three-quarter  housing  and  Fig.  129 
a  full  housing. 


Fig.  128. 


Fig.  129. 


The  circular  opening  in  the  housing  around  the  shaft  is 
the  inlet  to  the  fan,  the  air  being  thrown  by  centrifugal 
force  to  the  periphery  and  at  the  same  time  given  a  circular 
motion,  thus  leaving  the  fan  wheel  tangentially  through  the 
discharge  opening.  Fans  may  be  obtained  which  will  deliver 


218 


HEATING  AND  VENTILATION 


air  at  any  angle  with  the  horizontal.  They  may  have  two  or 
more  discharge  openings  (multiple  discharge  fans  as  shown 
in  Fig.  129),  and  double  side  inlets,  i.  e.,  air  entering  the  fan 
from  each  side  of  the  center.  Where  double  side  inlets  are 
used  they  are  smaller  than  the  single  side  inlet  for  the  same 
sized  fan.  All  fan  casements  should  be  well  riveted  and 
braced  with  angles  and  tee  irons.  The  shaft  should  be  fitted 
with  heavy  pattern,  adjustable  self-oiling  bearings,  rigidly 
fastened  to  the  casement  and  properly  braced.  The  thick- 
ness of  the  steel  used  in  the  casement  varies  according  to 
the  size  of  the  fan,  from  No.  14  to  No.  11  for  sizes  in  gen- 
eral use.  The  fan  wheel  should  be  well  constructed  upon  a 
heavy  spider  to  protect  against  distortion  from  sudden  start- 
ing and  stopping.  Fans  should  be  bolted  to  substantial 
foundations  of  brick  or  concrete.  When  connecting  fans  to 
metal  ducts  where  sound  from  the  fan  may  be  transmitted 
to  the  rooms,  the  connection  between  the  fan  and  the  duct 
should  be  made  through  flexible  rubber  cloth. 

The  terms  "Right  Hand"  and  "Left  Hand"  refer  to  the  position 
of  the  outlet  relatively  to  a  person  facing  the  pulley  or  driving  side 
of  the  fan,  i.  e.,  standing  on  the  pulley  or  driving  side  of  the  fan,  if 
the  discharge  is  to  your  right,  it  is  a  right  hand  fan;  if  the  discharge 
is  to  the  left,  it  is  a  left  hand  fan. 

123.  Fresh  Air  Entrance  to  Building 
and  to  Rooms: — Fresh  air  may  enter 
through  the  building  wall  near  the 
ground  level  or  it  may  be  taken  from  an 
elevation  through  a  stack  built  for  the 
purpose.  In  connection  with  washing 
systems  it  may  be  drawn  from  the  near- 
est and  most  convenient  source.  Where 
no  washing  or  cleaning  systems  are  in- 
stalled care  should  be  exercised  in  select- 
ing a  location  free  from  dust  and  other 
impurities.  Where  grills  or  shutters  are 
placed  in  the  opening,  they  are  planned 
to  obstruct  the  flow  of  the  air  as  little 
as  possible.  Plain  wire  screens,  %-  to 
l'-inch  mesh,  should  always  be  used  to 
keep  out  leaves,  birds  and  small  animals. 
In  exposed  places  stationary  slats  or 
grills  should  be  put  in  and  pitched  to 


Fig.  130. 


PLENUM  WARM  AIR   HEATING 


219 


keep  out  the  rain.     The  amount  of  slope  is  dependent  upon 

the  width  of  the  slat.     In  determining-  the  net  area  of  such  a 

grill  use   the   perpendicular   distance   between   the   slats   and 

not  the  vertical  spacing  (See  Fig.  130). 

Air  enters  the  rooms  through 
registers,  register  faces  or  de- 
flectors located  above  the  heads 
of  the  occupants.  Registers  are 
used  when  volumetric  regula- 
tion is  not  provided  for  else- 
where in  the  system.  Register 
faces  serve  no  economic  pur- 
pose and  are  put  in  for  orna- 
mentation. Deflectors  ^are  fre- 
quently substituted  for  register 
faces  to  direct  the  air  in  definite 
lines  about  the  room  thus  aid- 
ing uniform  circulation.  Where 
deflectors  are  used,  registers 
and  register  faces  are  omitted. 
Fig.  131  shows  the  air  inlet  to 

a  room  with  deflector  attachment. 

The  construction  of  the  dead  end  of  the  warm  air  stack 

is   important.     Never  finish   to  a  square  end  as   in   Fig.    132,   a. 

Always  have  an  easy  curve  as  in  &.     This  may  be  surfaced 


Fig.  131. 


Fig.  132. 

smooth  with  neat  cement  mortar  over  the  rough  bricks,  but 
a  better  way  is  to  have  tin  or  light  galvanized  iron  ends 
made  to  size  and  built  in  with  the  walls.  These  metal  ends 
are  still  more  efficient  when  fitted  with  splitters  as  shown  in 


HEATING  AND  VENTILATION 


c.  It  is  found  from  tests  that  much  more  air  is  delivered 
through  a  given  stack  for  the  same  power  expenditure 
when  these  are  used.  In  the  average  air  inlet  to  a  room  the 
lower  one-third  of  the  opening  is  almost  wholly  ineffective. 
Where  splitters  are  used  each  part 
of  the  opening  is  equally  effective. 
Vent  openings  are  placed  at  the 
floor  line  and  should  be  fitted  with 
registers  to  close  at  night  to  avoid 
heat  loss.  Behind  such  registers 
there  is  always  an  accumulation  of 
dust  and  dirt  which  is  very  unsani- 
tary. When  other  means  are  pro- 
vided for  closing  the  vents,  such  as 
dampers  within  the  stacks  or  at 
the  top  of  the  stacks  in  the  attic, 
registers  may  be  omitted  and  the 
vent  openings  curved  and  finished 
with  cement  flush  with  the  floor 
line,  as  in  Fig.  133.  This  permits 
the  ducts  to  be  more  easily  cleaned 
than  where  registers  or  faces  are 

used.  Automatic  air  control  from  the  fan  room  on  all  vents  that 
lead  to  the  attic  is  advisable.  In  buildings  having  air  supplied 
to  two  or  more  floors  it  is  frequently  necessary  to  condense 
the  stacks  into  the  smallest  space  possible.  Fig.  134  shows  a 
common  arrangement.  Notice  that  any  vertical  wall  space 
may  serve  both  as  a  heat  stack  for  a  lower  room  and  a  vent 
stack  for  an  upper  room.  To  accommodate  large  stacks  the 
thickness  of  the  wall  is  usually  increased.  All  offsets  must 
be  made  to  fit  the  sizes  of  the  standard  bricks  used. 

Allowable  velocities  for  net  openings  are  higher  than 
the  corresponding  velocities  in  furnace  systems  (See  Table 
XXIV.  Register  sizes  are  given  in  Table  19,  Appendix. 

124.  Heating  Surfaces: — Heating  surfaces  used  with 
plenum  systems  may  be  divided  into  two  classes:  pipe  coil 
surface  made  of  loops  of  1-  or  1^-inch  wrought  iron  or  steel 
pipe  and  cast  surface,  made  of  hollow  rectangular  castings 
provided  with  numerous  staggered  projections  to  increase  the 
outside  surface  and  provide  greater  air  and  iron  contact.  To 
make  a  heater  of  either  kind  of  surface,  successive  units  are 


I'LUXUM  WARM  AIR   HEATING 


221 


assembled  side  by  side,  until  the  requisite  total  area  and 
depth  have  been  obtained.  The  total  number  of  square  feet 
of  cast  or  pipe  coil  surface  exposed  to  the  air  determines  the 


total  number  of  heat  units  given  to  the  air  per  hour,  while 
the  depth  of  the  heater  and  the  spacing-  of  the  coils  control 
the  final  temperature  of  the  air  leaving-  the  heater.  Data 

upon  these  points  have 
been  obtained  through 
exhaustive  tests.  Each 
must  be  considered  in  de- 
signing the  heater  system 
(See  Arts.  136,  137,  139 
and  140). 

Pipe  coils  may  be  used 
with  any  steam  pressure 
but  cast  coils  should  never 
be  used  with  pressures 
exceeding  25  pounds  per 
square  inch  gage.  All 
plenum  heating  surfaces 
should  be  well  vented 

Fio.   ^  and    drained.      Ample    al- 

lowances   also    should    be 
made  for  expansion  and  contraction. 


222 


HEATING  AND  VENTILATION 


Fig.  136. 


Coil  surface  is  of  three  kinds:  that  having-  the  pipes 
inserted  vertically  into  a  horizontal  cast  iron  header  which 
forms  the  base  of  the  section  (Fig.  135);  that  having  the 
pipes  horizontal  between  two  vertical  side  headers  (Fig. 
136);  and  that  having  one  header  vertical  and  one  horizontal 

called  the  miter  coil  (Fig. 
137).  Sections  fitted  with 
pipe  coils  may  be  had  two, 
three  or  four  rows  of  pipes 
in  depth.  The  standard  num- 
ber of  roios  of  pipes  in  any  one 
section  is  four.  Sometimes 
these  pipes  are  spaced  in 
straight  lines  parallel  with 
the  wind  and  sometimes 
they  are  staggered.  Stag- 
gered spacing  increases  somewhat  the  friction  of  the  air 
current  and  the  power  of  the  fan.  Heat  efficiency  tests  of 
both  straight  and  staggered  spacings  show  little  difference. 
Coil  sections  represented  by  Figs.  136  and  137  have  better 
drainage  than  those  shown  by  Fig.  135.  In  the  latter  the 
condensation  must  flow  against  the  steam  or  be  carried  over 
with  it  to  the  return.  All  condensation  that  .collects  in  the 
supply  side  of  the  header  must  drain  to  the  return  side 
through  one  or  more  small  holes  in  the  division  plate.  This 
method  of  drainage  is  not  satisfactory  because  the  total 
area  of  the  openings  is  constant  and  the  amount  of  con- 
densation to  be  passed  is  vary- 
ing, thus  causing  a  clogging 

^      ,  by    extra    condensation     or    a 

ft-  short   circuiting1  of   the   steam 

to  the  return.  The  miter  sec- 
tion in  addition  to  perfect 
drainage,  has  perfect  expan- 
sion, permitting  every  pipe  to 
assume  any  position  necessary 
to  account  for  a  reasonable 
change  of  length  without 
causing  breaking  stresses  in 

f        JIIIIIIIIIIHHIIIIIillllllllllllllllllllllllimiv  the  pipe  threads- 

M_ J  I         Cast  iron  radiatini/  surfaces  for 

Fig.  137.  plenum    systems    are    cast    in 


PLENUM  WARM  AIR  HEATING 


223 


Steam  • 


Condensation" 
Fig.  138. 


units  called  sections,  and  these 
are  joined  top  and  bottom  by 
nipples  into  larger  units  called 
stacks,  quite  similar  in  all  re- 
spects to  a  direct  hot  water 
radiator.  Stacks  are  assembled 
one  in  front  of  another  in  the 
direction  of  the  air  current  thus 
forming  a  heater.  Fig.  138  shows 
a  heater  ten  sections  in  width 
and  two  stacks  in  depth.  Pro^- 
vided  the  conditions  demand  it, 
the  heater  may  be  built  two  or 
even  three  stacks  in  height, 
thus  doubling  or  tripling  the 
gross  wind  area  (See  Art.  140). 

Cast  iron  heaters  of  the  vento 
type  are  made  in  sizes  shown 
by  Table  XXIII.  It  is  unusual 
to  assemble  less  than  five  or 
more  than  twenty-five  sections 
to  the  stack.  By  the  proper  ad- 
justment of  number  of  sections 
to  the  stack  and  of  stacks  to 
the  heater,  any  requirement  of 
.plenum  system  may  be  met. 

Heaters  are  placed  on  either 
the  suction  or  force  side  of  the 
fan,  usually  the  former  in  dry- 


ing or  evaporating  plants  and  the  latter  in  heating  plants. 
Because  of  their  weight,  ample  and  firm  foundations  must  be 
provided,  with  metal  surface  on  top  of  foundation  to  permit 
expansion  movement.  In  most  installations  for  heating  pur- 
poses, where  both  tempered  and  heated  air  are  supplied,  the 
heater  is  raised  above  the  floor  18  to  30  inches  to  permit  an 
air  passage  and  damper  for  tempered  air. 

125.  Division  and  Location  of  Coil  Surface: — It  is  com- 
mon practice  to  install  heaters  for  plenum  systems  in  two 
parts,  known  as  tempering  coils  and  heating  coils.  The  total 
heating  surface  is  first  calculated  and  then  divided  into  tem- 
pering and  heating  coils  in  desired  proportions.  The  tem- 
pering coils  are  placed  in  the  air  passage  just  inside  the  in- 


!24  HEATING  AND  VENTILATION 

TABLE   XXIII. 
Vento  Cast-Iron  Heaters — Steam  or  Water. 


Narrow 

Sections 

Sq.  Ft.  per 
Section 

Height 

Width 

40   inch 

7.50 

41& 

6% 

50  inch 

9.50 

50g;} 

63/4 

60  inch 

11.00 

6GB 

6% 

Regular 

Sections 

30  inch 

8.00 

30 

9Vs 

40   inch 

10.75 

41& 

9% 

50  inch 

13.50 

50  §8 

9V8 

60   inch 

16.00 

60U 

9Vs 

72   inch 

19.00 

72 

9y8 

take  of  the  building  and  usually  contain  from  one-fourth  to 
one-third  of  the  total  heating  surface.  In  this  way  ex- 
tremely cold  air  is  tempered  before  it  reaches  the  fan  thus 
insuring  good  lubrication  and  preventing  an  accumulation 
of  frost  on  the  fan  blades,  which  would  seriously  interfere 
with  the  free  movement  of  the  air.  The  heating  coils  are 
placed  just  beyond  the  fan  on  the  force  side  (See  Figs.  139 
and  140). 

Combined  plenum  and  gravity~in direct  systems  (Fig.  141)  have 
been  installed  in  which  the  heating  coils  (tempering  coils 
placed  as  before)  have  been  divided  and  used  in  sections  at. 
the  base  of  the  stacks  leading  to  the  various  rooms.  Such 
an  arrangement  does  not  impair  the  plenum  system  and  has 
an  advantage  in  being  able  to  by-pass  the  air  through  the 
plenum  chamber  and  use  the  sectional  heaters  as  an  indirect- 
gravity  system  during  the  night  and  at  other  times  when  the 
fans  are  not  running.  With  the  coils  divided  as  stated  and 
the  same  amount  of  surface  put  in  the  indirect-gravity  coils 
as  would  be  required  in  the  plenum  heating  coils,  the  gravity 
system  will  temper  the  room  air  but  will  not  keep  the  rooms 
at  the  same  temperature  as  when  operating  with  the  fan, 
because  of  the  reduced  volume  of-  the  air  moving  and  the 
corresponding  drop  in  efficiency  of  the  heating  surface.  This 
difficulty  may  be  overcome  by  installing  more  indirect- 


PLENUM  WARM  AIR   HEATING 


225 


ELEVATION 


Fig.  139.  Fan  Room  Layout  with  Single  Ducts  along 
Basement  Ceiling-  and  all  Mixing-  Dampers  at  Plenum 
Chamber. 


HEATING  AND   VENTILATION 


Fig.    140.      Fan  Room   Layout   with   Double   Underground 
Ducts  and  Mixing  Dampers  at  Base  of  Room  Stacks. 


PLENUM  WARM  AIR  HEATING 


227 


Fig-.  141.     Fan  Room  Layout  with  Heating-  Coils  Divided 
into  Individual  Room  Heaters. 


228  HEATING  AND   VENTILATION 

gravity  heating-  surface.  In  many  plants  (school  buildings 
and  the  like)  a  moderate  temperature  (50°  to  60°)  through- 
out the  night  is  all  that  is  necessary  and  such  an  arrange- 
ment of  coil  surface  is  satisfactory  (See  Trans.  A.  S.  H.  & 
V.  E.,  Vol.  XIV,  p.  96;  Vol.  XVII,  p.  270;  Vol.  XVIII,  p.  370). 

In  large  installations  where  ventilation  is  of  prime  im- 
portance the  ideal  arrangement  is  the  split  system,  i.  e.,  ple- 
num heating  coils  sufficient  to  heat  the  ventilating  air  from 
the  outside  temperature  to  say  80°,  and  direct  radiation 
within  the  rooms  sufficient  to  keep  the  room  air  at  60°  dur- 
ing the  night  and  at  times  when  ventilation  is  not  needed. 
This  system  is  especially  adapted  to  schools  (Figs.  154  to 
156)  where  for  sixteen  hours  out  of  the  twenty-four  heating 
only  is  required.  During  the  eight  hours  when  air  circula- 
tion is  needed  the  amount  of  ventilating  air  may  be  regu- 
lated as  desired,  independent  of  the  heating.  In  the  split 
system  automatic  temperature  control  should  be  installed  as 
a  connecting  link  between  the  ventilating  and  heating  sys- 
tems. The  temperature  of  the  rooms  on  the  coldest  nights 
will  be,  say  60°.  The  radiators  will  be  in  service  until  with 
the  aid  of  the  plenum  system  (started  at  8  to  8:30  A.  M.) 
the  room  air  is  raised  to  70°  when  the  direct  radiation  is 
automatically  thrown  out  of  service.  The  radiators  continue 
automatic  action  in  connection  with  the  plenum  system  hold- 
ing the  room  temperatures  within  two  degrees  of  fluctuation 
(generally  69°  to  71°).  When  the  plenum  system  shuts 
down  all  radiators  throw  on  and  night  conditions  prevail. 

126.  Single  Duct  Plenum  System: — The  duct  systems 
that  carry  the  air  may  be  either  of  the  single  duct  or  double 
duct  type.  In  both  types  of  plants  the  fan  delivers  the  air 
to  a  small  room  known  as  the  plenum  chamber.  This  chamber 
is  divided  into  two  parts,  the  upper  one  (hot  air  chamber) 
receives  the  air  after  leaving  the  heating  coils;  the  lower 
one  the  air  that  has  been  warmed  by  the  tempering  coils. 
In  the  single  duct  system  (Fig-.  139)  a  single  metal  duct  is 
carried  from  the  base  of  each  vertical  heat  stack  to  this 
plenum  chamber  and  connected  to  both  hot  and  tempered 
air  through  a  mixing  damper  controlled  by  thermostat  from 
the  room  supplied.  Most  ducts  are  carried  along  the  base- 
ment ceiling  and  when  the  ceiling  height  is  sufficient  there 
is  a  false  ceiling  installed  below  the  ducts  for  artistic 
effect.  This  system  requires  a  complicated  network  of  dam- 


PLENUM  WARM  AIR  HEATING 


229 


Fig.  142. 

pers  and  ducts  at  the  plenum  chamber  which  to  a  certain 
degree  limits  its  use.  Fig-.  142  shows  a  single  duct  installa- 
tion applied  to  factories  of  several  stories. 

127.  Double  Duct  Plenum  System: — As  the  name  indi- 
cates, this  system  (Fig-.  140)  runs  all  ducts  in  pairs  (one 
above  the  other)  from  the  plenum  chamber  to  the  base  of 
each  vertical  room  stack.  The  upper  duct  carries  warm  air 
from  the  heating-  coils  while  the  lower  duct  carries  tem- 
pered air.  The  mixing  dampers  are  consequently  located 
at  the  base  of  the  vertical  room  stacks.  The  dampers  may 
be  hand  controlled  by  chain  pulls  from  the  rooms  above  or 
automatically  controlled  by  thermostats.  With  this  arrange- 
ment it  is  evident  that  the  principal  ducts  become  trunk  lines 
and  are  composed  in  a  minimum  of  space. 

Double  duct  systems  are  frequently  installed  as  sub- 
basement  systems,  as  compared  with  the  single  duct  systems 
which  have  usually  metal  ducts  along-  the  ceiling.  Such  ducts 
are  below  the  basement  floor  and  are  constructed  of  brick 
and  cement,  or  of  concrete,  about  4  inches  thick.  For  de- 
signs of  conduits,  ducts  and  dampers  see  Figs.  139,  140,  151 


230 


HEATING  AND  VENTILATION 


Fig.  143. 

and  154.  Fig-.  143  shows  a  complete  steel  housed  plenum 
unit  of  fan,  coils,  dampers  and  duct  connections.  For  shapes 
and  sizes  of  fans  see  manufacturers  catalog's. 

128.  Air  Washing  and  Humidifying-  Systems: — In  con- 
nection with  mechanical  warm  air  heating-  and  ventilating 
systems,  there  is  often  installed  apparatus  for  washing  and 
humidifying  the  air.  In  crowded  city  districts  where  the  air 
is  laden  with  dust,  soot,  the  products  of  combustion  and 
other  harmful  gases,  its  purification  and  moistening  becomes 
a  most  important  problem.  The  plenum  system  of  heating 
and  ventilating  lends  itself  most  readily  to  the  solution  of 
this  problem,  with  the  result  that  modern  practice  is  tend- 
ing more  each  day  toward  the  combined  installation  of  heat- 
ing", ventilating  and  humidifying  apparatus. 


r 


Fig.  144. 


PLENUM  WARM  AIR   HEATING 


231 


A  purifier  comprises  two  parts,  a  washer  and  an  eliminator 
(See  Fig-.  144).  The  washer  is  located  in  the  main  air  duct 
immediately  behind  the  tempering  coils,  and  provided  with 
sheets  or  sprays  of  water  through  which  the  air  must  pass. 
Having  caught  the  dust  particles  and  dissolved  some  of  the 
soluble  gases  from  the  air,  the  water  falls  to  a  collecting 
pan  at  the  bottom  of  the  spray  chamber,  and  from  there  is 
again  pumped  through  the  spraying  nozzles.  As  the  water 
becomes  too  dirty  or  too  warm,  a  fresh  supply  is  delivered 
to  the  collecting  pan.  A  small  independent  centrifugal 
pump  is  used  for  circulating  the  spray  water. 


Fig.  145.  Fig.  146. 

After  passing  through  the  washer,  the  air  next  encoun- 
ters the  eliminator,  the  purpose  of  which  is  to  remove  the 
surplus  moisture,  solids  and  water  particles  remaining  sus- 
pended in  the  air.  This  is  accomplished  by  baffle  plates 
(Fig.  145),  which  change  the  direction  of  the  air  many 
times  in  succession  and  cause  the  water  particles  and  solids 
to  impinge  upon  the  baffle  plates  and  fall  to  the  drip  tank. 
As  the  air  leaves  the  eliminator  and  enters  the  fan  it  may, 
with  good  apparatus,  be  relieved  of  98  per  cent,  of  all  dust 
and  dirt,  may  be  supplied  with  moisture  to  very  near  the 
saturation  point,  and  in  summer  time  under  favorable  con- 
ditions, may  be  cooled  from  5  to  15  degrees  lower  than  the 
outside  atmosphere.  This  is  due  to  the  cooling  effect  of 
vaporizing  part  of  the  water. 

A  purifier  designed  upon  different  lines  than  that  in  the 
last  figure  is  shown  in  Fig.  146.  In  this  the  air  makes  a 


232 


HEATING  AND  VENTILATION 


double  reverse  curve  and  passes  through  four  lines  of  spray 
before  reaching-  the  eliminator. 

Fig-.  147  represents  the  Zellweger  combination  fan  and 
purifier  which  has  proved  very  satisfactory  in  offices  and  small 
schools.  This  is  similar  to  the  ordinary  blower  fan  except- 
ing that  the  wheel  is  a  combined  filter  ring  and  eliminator. 
Water  may  be  circulated  entirely  or  in  part  by  the  tan- 


Fig.  147. 

gential  force  of  the  water  as  it  leaves  the  wheel.  Air  enters 
the  wheel  through  the  side  opening  and  in  passing  through 
the  wheel  rim,  which  is  composed  of  several  layers  of  fine 
meshed  wire  cloth  inside  the  curved  vanes  of  the  wheel,  it 
comes  in  contact  with  the  spray  water  from  four  spray 
heads.  The  outer  edges  of  the  blades  are  turned  to  form 
small  gutters  which  catch  the  water  and  direct  it  to  the 
large  end  of  the  wheel  (wheel  conical  on  surface)  to  the 
skimmer  and  collector  ring  for  recirculation  or  for  drainage. 
Full  or  three-quarter  housing,  single  or  double  inlet  and 
wheel  diameters  from  2.3  to  13  feet  may  be  obtained. 


PLENUM   WARM  AIR  HEATING  233 

An  air  washer  well  installed  and  maintained  may  be 
expected  to  remove  98  per  cent,  of  all  dust,  dirt,  soot,  etc.; 
to  lower  the  temperature  of  the  air  85  per  cent,  of  the  initial 
wet  bulb  depression;  to  raise  the  temperature  of  the  enter- 
ing- air  from  35°  to  any  temperature  up  to  60°  and  to  add 
the  necessary  moisture  to  obtain  any  relative  humidity  up  to 
75  per  cent,  when  the  rooms  are  70°;  and  to  control  the  rela- 
tive humidity  within  5  per  cent,  variation  when  the  wet  bulb 
temperature  of  the  air  entering  the  purifier  is  below  the  de- 
sired dew  point,  all  with  a  frictional  resistance  in  the  puri- 
fier not  to  exceed  .2  inch  water  gage. 

Special  air  cooling  plants  are  installed  in  connection 
with  the  plenum  system  of  ventilation,  whereby  refrigerated 
brine  is  circulated  in  the  regular  heating  coils.  (See  Trans! 
A.  S.  H.  &  V.  E.,  Vol.  XV,  p.  252). 


CHAPTER  XI. 


MECHANICAL   WARM  AIR   HEATING  AND   VENTILATION. 
FAN-COIL    SYSTEMS. 


AIR,    HEATING    SURFACE    AND    STEAM    REQUIREMENT. 
PRINCIPLES  OF   DESIGN. 

129.  Definition  of  Terms: — Some  of  the  technical  abbre- 
viations  that   are   frequently   used  are   the   following:      //    = 
B.  t.  u.  heat  loss  per  hour  by  heat  loss  formula,  Hv  =  B.  t.  u. 
heat  loss  per  hour  by  ventilation,  H'   =   total  B.  t.  u.  loss  — 
H  +  Hv,  Q   =   cubic  feet  of  air  used  per  hour  as  a  heat  car- 
rier   (calculated   from  H),   Q'    =    1800  N   =    cubic  feet   of  air 
used  in  obtaining  duct  sizes,  etc.,  when  air  for  ventilation  is 
in  excess  of  air  for  heating,  R  =  total  square  feet  of  heating 
surface   in   indirect  heaters,   f*    =    temperature   of  the   steam 
or  water  in  the  heaters,  t  =   highest  temperature  of  the  air 
at  the  register  (assumed  the  same  as  the  temperature  of  the 
air  upon  leaving  the  heater),  t'  =  temperature  of  the  air  in 
the  room,  U   =   temperature  of  the  air  at  the  register  when 
Q'    is   used   and   *   is   reduced    to   keep,   the   room    from    being 
overheated,   to    =    temperature   of   the  outside  air,   K   =    rate 
of  transmission  of  heat  through  the  coils,  N  =    the  number 
of  persons  to  be  provided  with  ventilation,  V   =   velocity  in 
feet  per  minute  and  v  =   velocity  in  feet  per  second.     Other 
abbreviations  are  explained  in  the  text. 

130.  Theoretical    Considerations: — For    illustrative    pur- 
poses, references  will  be  made  throughout  this  discussion  to 
a  sample  plenum  design,  Figs.  151,  152  and  153.     These  show 
the  essential  points  of  most  plenum  work  and  will  serve  as  a 
basis   for   the   applications.      In   any   plenum   design   the   fol- 
lowing   points   should    be    theoretically   considered    for    each 
room:  heat  loss,  cubic  feet  of  air  per  hour  needed  as  a  heat 
carrier    (this    should    be    checked    for    ventilation    and    the 
greater    value    used),    net    area    of    the    register    in    square 
inches,  catalog  size  of  the  register  and  area  and  size  of  the 
ducts.     In  addition  to  these  the  following  should  be  investi- 
gated  for   the   entire   plant:   size   of  the   main   leader   at   the 
plenum  chamber,  size  of  the  principal  leader  branches,  square 


PLENUM  WARM  AIR   HEATING  235 

feet  of  heating  surface  in  the  coils,  lineal  feet  of  coils, 
arrangement  of  the  coils  in  stacks  and  heaters,  horse-power 
capacity  and  revolutions  per  minute  of  the  fan  including 
sizes  of  the  inlet  and  the  outlet  of  the  fan,  horse-power  of 
the  engine  including  the  diameter  and  the  length  of  stroke, 
and  pounds  of  steam  condensed  per  hour  in  the  coils. 

Fresh  air  is  taken  into  the  building  at  the  assumed  low- 
est temperature,  to° ,  is  carried  over  heated  coils  and  raised 
to  t°  (in  certain  cases  to  tv°),  is  propelled  by  fans  through 
ducts  to  the  rooms  and  then  exhausted  through  vent  ducts 
to  the  outside  air.  It  is  the  object  of  this  section  to  so  dis- 
cuss this  cycle  that  the  principles  may  be  applied  to  gen- 
eral problems. 

131.      Heat   Loss   and  Cubic  Feet  of  Air  per  Hour: — It   is 

assumed  in  these  calculations  that  the  circulating  air  is  all 
taken  from  the  outside  and  thrown  away  after  being  used. 
Many  installations  have  arrangements  for  returning  part  or 
all  of  the  air  to  the  coils  and  reheating  it  as  an  economic 
method  of  operation  but  this  should  not  be  taken  into  con- 
sideration in  obtaining  the  sizes  of  the  heaters.  It  is  best 
to  design  the  plant  with  the  understanding  that  all  the  air 
is  to  be  thrown  away.  It  will  then  be  large  enough  for  any 
service  that  it  may  be  expected  to  handle.  Having  found  H 
by  some  acceptable  equation  (See  Art.  39),  the  total  heat 
loss  is 

(Q  or  Q')  (f  —  to) 

IV  -  H  +  -  -  (See  also  Arts.  42  and  50).     (61) 

55 

Assuming  to  =  0°  as  the  lowest  temperature  at  which  fresh 
air  will  be  admitted  (any  temperature  lower  than  this  would 
call  for  recirculated  air)  this  equation  reduces  to  H'  =  H  + 
1.27  (Q  or  Q').  To  determine  whether  Q  or  Q'  will  be  used 
find  Q  from  H,  Equation  33,  and  compare  with  Qf,  taking  the 
larger  value.  If  this  is  to  be  a  system  of  plenum  heating 
only,  let  t  =  140°,  tf  =  70°  and  to  =  0°,  then 

55  II  H  H 

N  =  -  —  =  approximately  (62) 

1800  (t  —  f)          2290  2300 

and  since  t  —  t'  =  t'  —  to,  Hf  =  2  H,  that  is  to  say,  the  heat 
given  off  from  the  air  in  dropping  from  the  register  tem- 
perature 140°  to  the  room  temperature  70°,  goes  to  the  radi- 
ation and  leakage  losses  //,  while  that  given  off  between  the 


236  HEATING  AND  VENTILATION 

inside  temperature  70°  and  the  outside  temperature  0°,  is 
charged  up  to  ventilation  losses  Hr.  Since  these  values  are 
equal,  Hf  =  H  +  Hv  =  2  H. 

APPLICATION. — Referring  to  Fig.  152,  room  15,  the  calcu- 
lated heat  loss  for  this  room,  with  t'  =  70°  and  to  —  0°,  is 
70224  B.  t.  u.  per  hour;  also,  if  t  —  140°,  Q  =  54775  cubic  feet 
per  hour.  Applying  Equation  61,  the  total  heat  loss  is 
140448  B.  t.  u.  per  hour.  With  54775  cubic  feet  of  air  sent 
to  the  room  per  hour,  this  provides  good  ventilation  for 
thirty  persons.  Suppose,  however,  that  fifty  persons  are  to 
be  provided  for;  this  requires  50  X  1800  =  90000  cubic  feet 
of  air  per  hour.  With  this  increased  number  of  people  in 
the  room,  the  total  heat  loss  is 

90000  (70  —  0) 

H'  =  70224  +  -  —  =  184864  B.  t.  u. 

55 

Find  H'  when  N  =   50  and  to  =  — 10°. 

132.     Temperature  of  the  Entering  Air  at  the  Register: — 

In  plenum  heating  the  registers  are  placed  higher  in  the 
wall  and  the  velocity  of  the  air  is  greater  than  in  furnace 
work.  Suppose  for  this  work  the  maximum  temperature  t  = 
140°  excepting  where  an  extra  amount  of  air  is  required  for 
ventilation  purposes,  in  which  case  the  temperature  must 
necessarily  drop  below  140°  in  order  that  the  room  will  not 
be  overheated,  then 

55  H 

t  =  t'   +  (63) 

Q' 

APPLICATION  1.  Referring  to  room  15  (compare  with  Art. 
52)  assuming  the  heat  loss  to  have  been  estimated  with  ven- 
tilating air  supplied  sufficient  for  50  persons,  90000  cubic 
feet  per  hour,  the  temperature  of  the  air  at  the  register  is 


90000 
Find  *  when  N  =  40  and  to  =  20°. 

APPLICATION  2. — Referring  to  room  12  and  assuming  200 
persons  in  the  room  with  360000  cubic  feet  of  air  per  hour, 
the  temperature  of  the  entering  air  will  be  89°. 

These  applications  do  not  take  into  account  the  heat 
given  off  by  the  audience,  which  would  permit  the  reduction 


PLK XI TM    \V  A  1 1 M    A  I  1 1    H  h]  A T I X(  \ 


of  the  entering-  air  somewhat  below  the  temperatures  stated 
(See  Art.  44). 

The  register  air  temperature  is  usually  taken  the  same 
or  slightly  less  than  the  temperature  of  the  air  upon  leav- 
ing the  coils.  If  this  room  were  to  be  the  only  one  heated, 
the  coils  would  be  figured  for  a  final  temperature  of  the  air 
at  113°,  but  other  rooms  may  have  air  entering  at  higher 
temperatures,  consequently  the  temperature  t  upon  leaving 
the  coils  should  be  that  of  the  highest  t  at  the  registers. 

133.  Cubic  Feet   of  Air   Needed   per  Hour: — The  amount 
of  air  needed  per  hour  as  a  heat  carrier  (compare  with  Art. 
50)   is 

55 II  H 

Q  =  ;  where  t  =  140  and  f  =  70,  Q  =  

t  —  t'  1.27 

If  extra  air  is  needed  for  ventilation,  Q'  =  1800  N. 

134.  Air    Velocities,    1,    in    the    Plenum    System: — Table 
XXIV  gives  the  velocities  in  feet  per  minute  that  have  been 
found   to   give   good   satisfaction    in   connection   with   blower 
systems. 

TABLE  XXIV. 
Air  Velocities  in  Plenum  Systems. 


Fresh 
air 
intake 

Over 
coils 

Main 
duct 
near 
fan 

Smaller 
branch 
ducts 

Stacks 

Reg'rs 
or  other 
open'gs 

Offices, 
schools,  etc. 

700  to  1000  T.  P.  M. 
Average  850  E.  P.  M. 

*i  *  2 

S^S 

*!§ 

PN&S 

o>  * 

£  2-a 

g  T3   02 

§8  >  > 
« 

1200  to 
1800 
say  1500 

800  to 
1200 
say  900 

500  to 

700 
say  600 

300  to 
400 
say  300 

Auditoriums, 
churches,  etc. 

1500  to 

2000- 
say  1800 

1000  to 
1500 
say  1200 

600  to 

800 
say  700 

400  to 
600 
say  400 

Shops  and 
factories 

1500  to 

3000 
say  2000 

1000  to 
2000 
say  1500 

600  to 
1000 
say  800 

400  to 
800 
say  500 

135.   Cross     Sectional    Area    of    Registers,    Ducts,    etc.: — 

With  the  above  velocities  in  feet  per  minute,  the  square 
inches  of  net  opening  at  any  part  of  the  circulating  system 
may  be  obtained  by  direct  substitution  in  the  general  equa- 
tion 

144  (QorQ') 

A  =   (Q  or  Q')    X  -     -  =  2.4  (64) 

60  F  F 


238  HEATING  AND   VENTILATION 

The  calculated  main  duct  sizes  refer  to  the  warm  air 
duct.  The  cold  air  duct  in  a  double  duct  system  need  not 
be  so  large  because  on  warm  days  when  only  tempered  air 
is  needed,  the  steam  may  be  turned  off  from  one  or  more  of 
the  heaters,  permitting-  the  warm  air  duct  to  furnish  what 
otherwise  would  be  required  from  the  cold  air  duct.  On 
account  of  this  flexibility  in.  the  warm  air  system  it  seems 
necessary  to  make  the  cold  air  duct  only  one-half  the  cross 
sectional  area  of  the  warm  air  duct.  For  convenience  of 
installation  it  would  be  well  to  make  the  former  the  same 
width  as  the  latter  and  one-half  as  deep,  unless  by  so  doing1 
the  cold  air  duct  becomes  too  shallow. 

APPLICATION. — Assuming  2000000  cubic  feet  of  air  passing 
through  the  main  heat  duct  at  A,  Fig.  151,  per  hour  at  the 
velocity  of  1800  feet  per  minute,  the  duct  is  approximately 
20  square  feet  in  cross-section,  or  2y2  by  8  feet.  The  two 
main  branches  at  B  carry  800000  cubic  feet  per  hour  each  at 
the  same  velocity  and  are  7.4  square  feet  in  area,  or  2  by  4 
feet.  The  same  branches  of  C  carry  400000  cubic  feet  per 
hour  each  at  a  velocity  of  1500  feet  per  minute  and  are  4.4 
square  feet  in  area,  or  2  by  2%  feet,  and  branch  D  carries 
300000  cubic  feet  at  a  velocity  of  1200  feet  per  minute  and  is 
iy2  by  2%  feet. 

The  stack  sizes  are  first  calculated  for  a  velocity  of  600 
feet  per  minute  and  then  made  to  fit  the  laying  of  the  brick 
work  such  that  the  velocities  are  600  feet  per  minute  or  less. 
The  net  register  is  calculated  for  an  air  velocity  of  300  feet 
per  minute  and  the  gross  registers  are  taken  1  to  1.5  times 
the  net  area  (the  smaller  value  is  used  with  splitters  and 
diffusers). 

136.  Final  Air  Temperatures: — Since  the  amount  of 
heat  transmitted  is  directly  proportional  to  the  difference  of 
temperature  between  the  two  sides  of  the  metal,  the  first 
coils  in  a  heater  are  the  most  efficient,  this  efficiency  drop- 
ping off  rapidly  as  the  air  becomes  heated  in  passing  over 
the  coils.  Final  temperatures  for  different  numbers  of  coil 
sections  in  banks  have  been  found  by  experiment  and  may 
be  taken  from  Table  XXV  (See  also  Table  XXIX). 


PLENUM  WARM  AIR   HEATING 


239 


TABLE  XXV. 

Temperatures  of  Air  upon  Leaving  Coils,  Steam  227°, 
Air  entering-  at  0°. 


Sections 

No.  of 
rows 

Velocities  of  air  through  coils  in  F  P.  M. 

800 

1000 

1200 

1500 

J 

4 

42 

33 

28 

23 

9 

8 

71 

62 

56 

52 

3 

12 

96 

87 

80 

75 

4 

16 

11!) 

108 

101 

93 

5 

20 

136 

125 

116 

108 

6 

24 

153 

140 

131 

120 

7 

28 

1<>9 

155 

143 

131 

8 

32 

183 

166 

154 

141 

These  temperatures  may  be  increased  about  10  per  cent, 
for  20  pounds  gage  pressure. 

Table  XXVI  shows  similar  results  quoted  for  the  Vento 
cast  iron  heaters. 

TABLE  XXVI. 

Temperature  of  Air  upon  Leaving  Vento  Coils,  Steam  227°. 
Regular  and  Narrow  Sections,  5  Inch  Centers. 

Velocities  of  air  through  coils  in  F.  P.  M. 


stacks 

in 

800 

1000 

1200 

1400 

depth 

Ent.  Temp. 

0° 

-10° 

-20° 

0° 

-10° 

-20° 

0° 

-10P 

-20° 

0° 

-10° 

-20° 

1 

Reg. 

38 

35 

3-? 

Nar. 

9 

Reg. 

68 

6<> 

55 

6" 

56 

49 

5« 

51 

44 

*Vl 

47 

40 

Nar. 

51 

<n 

36 

46 

38 

31 

-13 

35 

40 

39 

3 

Reg. 

03 

87 

89 

86 

80 

75 

81 

75 

60 

76 

70 

64 

Nar. 

70 

64 

58 

65 

58 

t>9 

61 

54 

47 

57 

5O 

43 

4 

Reg. 

113 

108 

103 

106 

101 

06 

TOO 

% 

00 

05 

80 

84 

Nar 

88 

83 

77 

8? 

76 

70 

77 

70 

64 

79 

65 

50 

5 

Reg! 

190 

196 

122 

12? 

118 

114 

115 

111 

1O7 

100 

105 

100 

Nar. 

1O3 

08 

03 

06 

01 

86 

00 

84 

70 

85 

70 

74 

6 

Reg. 

143 

140 

137 

135 

139 

"|9Q 

190 

T>5 

1?1 

1^3 

no 

m 

Nar.   _ 

115 

111 

107 

108 

103 

00 

10^ 

07 

09 

07 

09 

87 

7 

Reg. 

154 

15? 

150 

147 

144 

141 

140 

137 

134 

135 

131 

198 

Nar.    

1^7 

19,4 

1W 

19/> 

116 

11? 

114 

100 

105 

108 

103 

00 

240  HEATING  AND  VENTILATION 

137.     Square  Feet  of  Heating   Surface,  R,  in  the   Coil*: — 

To  determine  the  number  of  square  feet  of  heating  surface 
in  the  coils  of  an  indirect  heater,  the  following  equation  may 
be  used: 

H' 

R  =  (65) 


Rule. — To  find  the  square  feet  of  coil  surface  in  an  indirect 
heater,  divide  the  total  heat  loss  from  the  building  in  B.  t.  u.  per 
hour  by  the  rate  of  transmission  multiplied  by  the  difference  between 
the  inside  and  the  average  outside  temperatures  of  the  coils. 

Equation  65  presupposes  a  uniform  rise  in  the  tempera- 
ture of  the  air  as  it  passes  over  the  coils,  i.  e.,  if  the  air  is 
heated  from  0°  to  140°  in  passing  over  a  heater  24  pipe  rows 
deep,  at  the  sixth  row  the  temperature  would  be  35°,  at  the 
twelfth  row  70°,  and  at  the  eighteenth  row  105°.  It  is  found 
that  this  is  not  the  case  but  that  the  rise  is  more  rapid  in 
passing  over  the  first  part  of  the  heater,  gradually  falling 
off  to  the  end  of  the  heater  according  to  the  logarithmic 
curve.  The  mean  temperature  difference  between  the  inside 
and  the  outside  of  the  heater  instead  of  coming  from  an 
arithmetical  mean  as  given  within  the  brackets,  Equation 

(f)«     \ 
-    I  and  the  total  number 

of  square  feet  of  radiation  in  the  the  heater  is 

R  = (66) 


/      9«  —  Qi       \ 

\  log,  (e«/e«o/ 


where  6m  =  mean  temperature  difference,  0«  =  temperature 
difference  at  the  entering  end  and  6&  =  temperature  differ- 
ence at  the  leaving  end.  For  full  discussion  of  Equation  66 
see  Elements  of  Heat  Power  Engineering,  Hirshfeld  and 
Barnard,  Chapter  XXXV.  Equations  65  and  66  give  approx- 
imately the  same  results,  as  shown  by  Equations  67  and  68. 
The  first  is  more  easily  applied  and  is  recommended  for 
ordinary  heater  calculations.  These  equations  are  rational 
and  the  terms  indicated  are  readily  apparent  excepting  per- 
haps the  value  K.  Various  experimenters  have  done  exten- 
sive work  toward  establishing  this  and  a  few  of  their  re- 
sults will  be  briefly  summarized. 


PLENUM  WARM  AIR  HEATING 


241 


Prof.  Carpenter  quotes  extensively  from  experiments 
with  coil  heaters  in  blower  systems  and  summarizes  in  the 
equation  K  —  2  +  1.3  Vv  where  v  is  the  average  velocity  of 
air  over  the  coils  in  feet  per  second.  With  coil  velocities  in 
common  use,  800  to  1400  feet  per  minute,  this  equation  gives 
K  from  7  to  8.5,  which  are  very  conservative  and  safe  values. 

Mr.  F.  R.  Still  gives  the  following  equation  for  the  total 
B.  t.  u.  transmitted  per  square  foot  per  hour,  between  the 
temperature  of  the  steam  and  that  of  the  entering  air,  total 
B.  t.  u.  transmitted  =  c  Vt'"(^  —  to),  (Table  XXVIII),  in  which 
r  is  velocity  in  feet  per  second  and  c  is  a  constant  which 
varies  with  the  number  of  sections  as  shown  in  Table  XXVII. 

TABLE  XXVII. 
Values  of  c. 


Safe  factor 

Max.  factor 

1  section      4 

rows  of 

pipe 

3  45 

4  40 

2  sections    8 

rows  of 

pipe 

3  00 

3  40 

3  sections  12 

rows  of 

pipe 

2.63 

2.85 

4  sections  16 

rows  of 

pipe 

2.33 

2.45 

5  sections  20 

rows  of 

pipe.-    

2.12 

2.20 

6  sections  24 

rows  of 

pipe.         _____    __ 

1.96 

.05 

7  sections  28 

rows  of 

pipe 

1  80 

95 

8  sections  32 

rows  of 

pipe 

1  65 

85 

!)  sections  36 

rows  of 

pipe 

1.52 

.80 

10  sections  40 

rows  of 

pipe    _ 

1.40 

.75 

From  the  above  values  of  c,  Table  XXVIII  has  been  com- 
piled, assuming  ts  =   227,  to  =  0  and  c  —  safe  factor. 

TABLE  XXVIII. 


Total  transmission  in  B.  t.  u.  per  sq.  ft.  per  hour. 


Velocity 

tx  rr  227;  to  —  0. 

of  air 

in  feet 

Rows  of  pipe  deep 

4 

8 

12 

16 

20 

24 

28 

32 

800 

2840 

2470 

2164 

1920 

1750 

1606 

1450 

1360 

1000 

3200 

2790 

2440 

2170 

1900 

1810 

1670 

1535 

1200 

3500 

3040 

2670 

2360 

2150 

1980 

1825 

1678 

1400 

3783 

3290 

2884 

2555 

2325 

2138 

1974 

1809 

242 


HEATING  AND  VENTILATION 


Since   the   values   given   in    Table   XXVIII   are    the    total 
B.   t.   u.   transmitted   per   square   foot   per   hour   for   different 

(t  +  to 
ts |,  A'  is  found  to  vary 


/              t  +  to  \ 
—  to)  =  K  I  t, J  ,  K  is 


between  10.5  and  15  with  an  average  of  approximately  12. 

Table  XXIX  by  Mr.  C.  L.  Hubbard  shows  efficiencies  that 
are  less  than  those  just  considered.  These  agree  more  nearly 
with  average  practice. 

TABLE  XXIX. 
Efficiencies  of  Forced  Blast  Pipe  Heaters,  and  Temperatures 

of  Air  Delivered. 
Velocity  of  air  over  coils  at  800  feet  per  minute. 


Rows 
of  pipe 
deep 

Temp,  to  which  the  air 
will  be  raised  from  zero 

Efficiency  of  the  heating  surface 
in  B.  t.  u.  per  sq.  ft.  per  hr. 

Steam  pressure  in  heater 

Steam  pressure  in  heater 

51b. 

20  lb. 

60  lb. 

5  lb. 

20  lb. 

60  lb. 

4 

30 

35 

45 

1600 

1800 

2000 

6 

50 

55 

65 

1600 

1800 

2000 

8 

65 

70 

85 

1500 

1650 

law 

10 

80 

90 

105 

1500 

1650 

1850 

12 

95 

105 

125 

1500 

1650 

1850 

14 

105 

120 

140 

1400 

1500 

1700 

16 

120 

130 

150 

1400 

15GO 

1700 

18 

130 

140 

160 

1300 

1400 

1600 

20 

140 

150 

170 

1300 

1400 

1600 

For  a  velocity  of  1000  feet  per  minute  multiply  the 
temperatures  given  in  the  table  by  0.9  and  the  efficiencies 
by  1.1. 

Perhaps  the  most  extensive  work  along  this  line  has 
been  done  by  Messrs.  Willis  H.  Carrier  and  F.  L.  Busey.  For 
details  see  Trans.  A.  S.  H.  &  V.  E.,  Heat  Transmission  with 
Indirect  Radiation  Vol.  XVIII,  p.  172.  From  these  experi- 
ments K  varied  from  9  to  13  for  velocities  from  800  to  1400 
feet  per  minute. 

When  estimating  plenum  heating  surface  it  is  well  to 
remember  that  after  a  coil  has  been  in  service  for  a  time  it 


PLENUM  WARM   AIR   HEATING  243 

becomes  somewhat  less  efficient  than  while  clean  and  new, 
also  that  even  though  the  very  best  arrangements  for  air 
removal  are  provided,  these  often  fail  or  work  with  lessened 
efficiency.  In  general,  even  though  transmission  tests  show 
rates  of  transmission  as  high  as  12  or  13  it  is  much  safer  to 
take  a  lower  value  for  average  conditions.  Assuming  for 
illustration  A'  =  8.5  and  T7  —  1000  as  the  best  values  to  use; 
also  ts  =  227  (5  pounds  gage  pressure),  t  —  140  and  to  —  0, 
Equations  65  and  66  become 

H'  H' 

R  =  -  (67) 

140  +  0    \      1335 

5. 5 


/ 

(227- 


Hf  H' 

R  =  -  (68) 

8.5  (227  —  87)  1240 


loge  227/87 

Note. — At  the  assumed  rate  of  transmission,  8.5,  each 
square  foot  of  heating  surface  is  equal  to  5  square  feet  of 
direct  radiation.  This  is  due  to  the  increased  velocity  of  air 
over  the  radiating  surface. 

Cast  iron  heaters  are  being  increasingly  used  for  low  pres- 
sure indirect  heating,  replacing  pipe  coil  heaters.  The  effi- 
ciency of  these  heaters  is,  according  to  tests,  about  the  same 
as  that  of  the  pipe  coil  heaters  and  hence  Equations  65  and 
66  will  apply  to  both  pipe  and  cast  heaters.  For  more  com- 
plete data  on  efficiencies  and  final  temperatures  than  given 
in  Table  XXVI  see  American  Radiator  Co.'s  Engineers'  Data, 
Vento  Heaters. 

APPLICATION  1.  Where  heating  only  is  considered. — Referring 
to  Table  XXXV,  let  H  for  the  entire  building  (to  =  0°)  = 
1483251  and  t  =  140.  Then  from  Art.  133,  Q  =  1156935;  by 
Equation  61,  H'  =  2966502;  and  Equation  67,  the  coil  sur- 
face is 

2966502 

R  =  =   2222  sq.  ft. 

140  +  0 


/ 

(227- 


With  three  lineal  feet  of  1-inch  pipe  per  square  foot  of  sur- 
face we  have  6666  lineal  feet  of  coils  in  the  heater. 

APPLICATION  2.     Where  heating  and  ventilation  are  combined. — 
Assume  1100  people  in  the  building  on  a  zero  day  and  Q'   = 


244  li  KATI\<;    AND    V  KXT  FLATK  >X 

2000000.      Then   H'    =    1483251    +    1.27    X    2000000    =    4023251, 
with  equal  distribution  of  air,  t  =.  111,  and 

4023251 

R   =  -  -  =   2758  sq.  ft.  =   8274  lin.  ft.  coils. 

111  +  0 


/  111 

(227- 


APPLICATION  3.  Where  hcatiin/  and  ventilation  arc  separate. 
Split  system. — With  the  same  number  of  people  in  the  building 
as  given  in  Application  2,  the  heat  loss  H  may  be  supplied  by 
direct  radiation  and  Hv  by  fan  coils.  In  this  case 

2540000 
Rr  =  -  =  1597  sq.  ft.  =  4791  lin.  ft.  coils. 

80  +  0 


Final  temperature  80°  (F  =  1200)  gives  three  sections  of 
regular  vento  (12  rows  of  coils)  at  0°  outside  (See  Table 
XXVI).  This  gives  opportunity  of  reducing  the  direct  radi- 
ation to  give  t  =  60°  (See  also  Art.  140).  In  applying  Equa- 
tion 65,  t  is  usually  considered  140°.  Conditions  may  exist, 
however,  when  this  should  change.  For  illustration,  suppose 
that  in  a  certain  building  most  of  the  rooms  are  to  be  venti- 
lated and  that  these  rooms  will  have  large  amount  of  air 
delivered  at  low  temperatures  (Application  2).  In  such  a 
case  it  may  be  economy  to  raise  the  air  for  all  rooms  to  the 
lower  temperature  and  supply  more  air  to  those  rooms  that 
would  otherwise  b.e  heated  with  air  at  140°,  than  to  put  in  a 
heater,  large  enough  to  heat  all  the  air  to  140°  and  then 
dilute  with  large  amount  of  cold  air  to  lower  the  tempera- 
ture. Again,  suppose  that  a  school  building  contains,  in 
addition  to  the  regular  class  rooms,  laboratories,  etc.,  and 
auditorium  and  gymnasium,  the  two  together  requiring  an 
amount  of  air  sufficient  to  justify  a  separate  fan  system  (a 
condition  which  frequently  exists).  It  would  be  economy 
to  separate  the  heating  system  for  these  rooms  from  the 
rest  of  the  building  because  of  the  comparatively  short  time 
the  rooms  are  in  use.  When  not  in  use  either  fan  unit  may 
be  shut  down  without  interfering  with  the  other  unit,  thus 
approaching  a  higher  operating  efficiency. 

138.     Approximate  Rules  for  Plenum  Heating  Surfaces: — 

The  following  approximate  rules  are  sometimes  used  in 
checking  up  heating  surface  in  the  coils.  These  should  be 
used  with  caution. 


PLENUM  WARM  AIR   HEATING  245 

Rule  1.  "Allow  one  lineal  foot  of  1-inch  pipe  for  each,  65  to 
125  cubic  feet  of  room  space,  65  for  office  buildings,  schools,  etc.,  and 
125  for  shops  and  laboratories."  Since  this  building-  (Fig.  151) 
has  approximately  500000  cubic  feet  of  room  space,  it  gives 
7700  lineal  feet  of  1-inch  pipe  in  the  heater. 

Rule  2. — "Allow  200  lineal  feet  of  1-inch  pipe  for  each  1000 
cubic  feet  of  air  per  minute  at  a  velocity  of  1500  feet  per  minute." 
Applying  to  the  above  building'  when  the  air  moves  over  the 
coils  at  1000  feet  per  minute,  the  heated  surface  is  only 
about  four-fifths  as  valuable  and  would  require  250  lineal 
feet  per  each  1000  cubic  feet  of  air  per  minute.  This  g-ives 
8333  lineal  feet  of  coils. 

139.  Arrangement  of  Coils  in  Pipe  Heaters: — Coil  sec- 
tions are  arranged  in  two,  three  and  four  rows  of  pipes  per 
section.  Unless  special  reference  is  made  to  this  point,  the 
latter  value  is  understood.  Having  found  R  for  the  heater, 
obtain  from  the  temperature  tables  the  number  of  pipe  rows 
or  sections  deep  the  heater  will  need  to  be  to  produce  the 
desired  t°.  Next,  find  the  net  wind  area  across  the  coils  by 
dividing  the  total  air  moved  by  the  assumed  velocity  of  the 
coils.  From  the  net  wind  area  find  the  gross  cross  sectional 
area  of  the  heater  by  the  relation  commonly  used  by  manu- 
facturers— 

Gross  wind  area  =  2.5  times  net  wind  area. 
From  the  gross  area  the  size  of  the  heater  may  be  selected. 

APPLICATION  1.— In  Art.  137  let  R  -  2222,  Q  =  1156935, 
V  —  1000  (deep  heater)  and  *  =  140.  From  Table  XXV  the 
heater  will  require  24  rows  of  coils  in  depth  to  give  the  re-" 
quired  temperature.  The  net  area  will  be  1156935  -^-  (60  X 
1000)  =  19.3  sq.  ft.,  the  gross  area  will  be  2.5  X  19.3  —  48.25 
sq.  ft.  and  the  heater  size  will  probably  be  selected  6  ft.  x 
8  ft.  Check  for  R  by  second  method,  following  Application  3. 

APPLICATION  2. — Let  R  =  2758,  Q'  —  2000000,  V  =  1000 
(deep  heater)  and  t  =  111.  Find  the  heater  16  +  say  18 
rows  deep;  net  area  —  33.3  sq.  ft.;  gross  area  =  83.3  sq.  ft.; 
and  size  of  heater  =r  9  ft.  x  9  ft.  or  2  divisions  each  6  ft.  x 
7  ft.  Check  for  R  as  in  Application  1. 

APPLICATION  3.— Let  R  =  1597,  Q'  =  2000000,  V  —  1200 
(shallow  heater)  and  t  =  80.  Find  the  heater  12  rows  deep; 
net  area  =  27.8  sq.  ft.;  gross  area  =  69.5  sq.  ft.;  and  size  of 
heater  8  ft.  x  8.75  ft. 


246  HEATING  AND  VENTILATION 

A  second  method  of  obtaining  pipe  coil  heater  sizes  is  as 
follows:  having  found  R,  obtain  the  square  feet  of  heating 
surface  in  any  one  row  of  coils  across  the  heater  by  dividing 
R  by  the  number  of  rows  in  depth  (in  the  applications,  24, 
18  and  12).  Then  from  the  usual  relations  existing  between 
net  area,  gross  area  and  heating  surface  per  row  obtain  the 
size  of  the  heater.  Let  the  net  area  between  the  tubes,  N.  A., 
the  space  occupied  by  the  tubes,  T.  A.,  and  the  gross  cross 
sectional  wind  area  through  the  tube,  G.  W.  A.,  be  respectively 

Q  or  Q'  Q  or  Q'  Q  or  Q' 

N.  A.  —  —       — ;  T.  A.  =  —       — ;  and  G.  W.  A.  =  (69) 

607  40  V  .247 

Since  the  cross  sectional  space  T.  A.  occupied  by  the  tubes 
is  to  the  coil  surface  per  row  as  1  :  3.1416,  the  total  coil  sur- 
face in  one  row  of  tubes  is 

3.1416  (QorQ')  (Q  or  <?') 

Rl  =  — =   .08 


40  7  7 

Reduced  to  the  basis  of  the  net  area,  N.  A.,  we  have 

RI  =  4.8  times  N.  A.  (70) 

For  illustration,  when  substitution  is  made  in  the  three 
applications  just  cited  we  have:  first,  R  (per  row)  —  &2.6, 
Jf.  A.  =  92.6  -r-  4.8  =  19.3,  G.  A.  =  2.5  X  19.3  =  48.25  and  the 
size  of  the  heater  is  6  ft.  x  8  ft.;  second,  R  (per  row)  —  153, 
N.  A.  =  32,  G.  A.  =  80  and  the  size  of  the  heater  is  9  f t.  x  9 
ft.;  third,  R  (per  row)  =  133,  N.  A.  =  28,  G.  A.  =  70  and  the 
size  of  the  heater  is  8  ft.  x  8.75  ft. 

Slight  variations  occur  in  checking  between  the  two 
methods  because  of  the  difficulty  in  selecting  the  exact  num- 
ber of  rows  of  coils  to  fit  the  final  temperatures.  Either  of 
the  two  methods  as  shown  above  for  determining  the  size  of 
the  coil  heater  will  give  good  practical  results. 

Assembled  sections  of  pipe  coil  heaters  are  supplied 'by 
manufacturers  from  the  smallest  size  of  3  f  t.  x  3  ft.,  to  the 
largest  size  of  10  ft.  x  10  ft.,  these  dimensions  being  those  of 
the  gross  cross  sectional  area,  and  not  overall  dimensions. 
Between  the  two  limits,  both  height  and  breadth  usually 
vary  by  6  inch  increments.  For  exact  sizes,  consult  dimen- 
sion tables  in  manufacturers'  catalogs. 

140.  Arrangement  of  Sections  and  Stacks  in  Vento  Cast 
Iron  Heaters: — Referring  to  Applications  1,  2  and  3,  Art.  139, 
find  the  number  of  stacks  deep,  the  number  of  stacks  high, 


PLENUM  WARM  AIR  HEATING  247 

the  number  of  sections  to  the  stack  and  the  size  of  the 
heater  as  compared  with  each  application  in  coil  heaters. 

APPLICATION  1. — R  =  2222  and  N.  A.  =  19.3.  From  Table 
XXVI  the  number  of  stacks  deep  (regular,  t  =  140  and  to  = 
0)  =  6.  From  Table  53,  Appendix,  either  of  the  following 
arrangements  will  give  the  required  N.  A:  (a)  one  stack 
high,  60  in.  section,  21  sections  wide;  size  of  heater  105  in. 
wide  x  60  in.  high  x  55  in.  deep.  Check  R  =  336  X  6  =  2016 
sq.  ft.;  (b)  a  40  in.  stack  above  a  50  in.  stack,  14  sections 
wide;  size  of  heater  70  in.  x  90  in.  x  55  in.  Check  R  =  (189  + 
150.5)  X  6  =  2037  sq.  ft.;  (c)  a  40  in.  stack  above  a  40  in. 
stack,  16  sections  wide;  size  of  heater  80  in.  x  80  in.  x  55  in. 
Check  R  =  2  X  172  X  6  =  2064  sq.  ft. 

APPLICATION  2. — R  =  2758  and  N.  A.  =  33.3.  From  the 
same  tables  (regular,  *  =  111  and  to  —  0)  the  number  of 
stacks  deep  =  5  and  the  following  arrangements  will  give 
the  required  N.  A.:  (a)  a  60  in.  stack  above  a  60  in.  stack, 
18  sections  wide;  size  of  heater  90  in.  x  120  in.  x  46  in.  Check 
R  —  2  X  288  X  5  =  2880  sq.  ft.;  (b)  a  40  in.  stack  above  a 
60  in.  stack,  21  sections  wide;  size  of  heater  105  in.  x  100  in.  x 
46  in.  Check  R  =  2808  sq.  ft. ;  (c)  a  40  in.  stack  above  a  50 
in.  stack,  23  sections  wide;  size  of  heater  115  in.  x  90  in.  x 
37  in.  Check  R  =  2789  sq.  ft. 

APPLICATION  3. — R  =  1597  and  N.  A.  =  27.8.  Regular  sec- 
tions, t  =  80  and  to  =  0,  find  number  of  stacks  deep  —  3  and 
the  following  arrangements  of  heaters:  (a)  a  50  in.  stack 
above  a  60  in.  stack,  17  sections  wide;  size  of  heater  85  in.  x 
110  in.  x  28  in.  Check  R  —  1505  sq.  ft.;  (b)  a  40  in.  stack 
above  a  60  in.  stack,  19  sections  wide;  size  of  heater  95  in.  x 
100  in.  x  28  in.  Check  R  =  1525  sq.  ft.;  (c)  a  40  in.  stack 
above  a  50  in.  stack,  21  sections  wide;  size  of  heater  105  in.  x 
90  in.  x  28  in.  Check  7?  =  1527  sq.  ft. 

Other  arrangements  than  the  above  may  be  made  to  suit 
the  space  set  aside  for  the  heater  in  the  building  plan.  It 
will  be  noticed  that  the  vento  coils  as  taken  from  the  tables 
check  somewhat  below  the  calculated  R.  Where  space  will 
permit  add  enough  sections  to  the  width  of  the  heater  to 
keep  the  total  surface  up  to  the  calculated  R  and  permit  the 
velocity  of  the  air  over  the  coils  to  drop  correspondingly. 

141.  Use  of  Hot  Water  In  Indirect  Coils: — In  most  cases 
low  pressure  steam  is  used  as  a  heating  medium  in  indirect 
heaters.  It  is  possible  to  use  hot  water  where  a  good  supply 


248  HEATING  AND  VENTILATION 

is  available.  In  such  an  arrangement  the  coils  will  be  cal- 
culated from  Equation  65,  using  all  values  the  same  as  for 
steam  excepting  t*,  which  will  be  replaced  by  the  average 
temperature  of  the  water.  The  piping  connections  and  the 
arrangement  of  the  coils  will  follow  the  same  general  sug- 
gestions as  already  stated  for  direct  heating. 

142.  Pounds  of  Steam  Condensed  per  Square  Foot  of 
Heating  Surface  per  Hour: — From  Art.  137  the  number  of 
pounds  of  condensation  per  hour  per  square  foot  of  surface 
in  the  coils  is 

H' 

m  = (71) 

A*  X  heat  given  off  per  pound  of  condensation 

APPLICATION. — Let  R  =  2758  and  //'  =  4023251;  also  let  1 
pound  of  dry  steam  at  5  pounds  gage  in  condensing  to  water 
at  212°  give  off  1156  —  180  =  976  B.  t.  u.  Then 

4023251 

m  =  =  1.5  pounds. 

2758   X   976 

This  amount  is  an  average  of  all  the  coils.  The  first  and 
last  sections  in  any  bank  may  vary  above  or  below  this 
amount  33  per  cent.  The  first  coils  will  condense  as  much 
as  2  pounds  of  steam  per  square  foot  of  surface  per  hour 
under  heavy  service. 

148.  Pounds  of  Dry  Steam  Needed  in  Excess  of  the  Ex- 
haust Steam  Given  Off  from  the  Engine: — In  all  steam  driven 
plenum  systems  it  is  economy  to  use  the  exhaust  steam  from 
the  power  unit  as  a  partial  supply  for  the  coils.  Let  the 
heating  value  of  the  exhaust  steam  from  the  engine  be  85 
per  cent,  of  that  of  good  dry  steam  (See  Arts.  164  and  172); 
also  let  the  engine  use  40  pounds  of  dry  steam  per  horse- 
power hour  in  driving  the  fan.  From  Art.  153  the  engine 
will  use  40  X  13.7  =  548  pounds  of  steam  per  hour  and  the 
heating  value  will  be  976  X  .85  =  830  B.  t.  u.  per  pound  or 
830  X  548  =454840  B.  t.  u.  total  per  hour.  Then  4023251  — 
454840  =  3568411  B.  t.  u.  and  3568411  -=-  976  =  3657  pounds 
of  steam.  The  boiler  will  then  supply  to  the  engine  and 
coils  3657  +  548  =  4205  pounds  of  steam  total  and  will  rep- 
resent 4205  ^-  30  =  140  boiler  horse-power. 


CHAPTER  XII. 


MECHANICAL,  WARM    AIR   HEATING  AND 
VENTILATION.      FAN-COIL    SYSTEMS. 


PRINCIPLES   OF    THE    DESIGN,    CONTINUED. 
FANS  AND  FAN  DRIVES. 

144.  Theoretical  Air  Velocity: — The  theoretical  velocity 
of  air  flowing  from  any  pressure  pa  to  any  pressure  pit,  is 
obtained  from  the  general  equation  v  =  V2#ft,  where  v  is 
given  in  feet  per  second,  g  =  32.16  and  h  =  head  in  feet  pro- 
ducing flow.  The  latter  value  may  be  easily  changed  from 
feet  of  head  to  pounds  pressure  and  vice  versa. 

When  exhausting  air  from  any  enclosed  space  into 
another  space  containing  air  at  a  less  density,  the  force 
which  causes  movement  of  the  air  is  pa  —  pit  =  p*.  Pressures 
may  be  taken  by  any  standard  type  of  pressure  gage.  These 
show  pressures  above  the  atmosphere.  When  exhausting 
from  any  container  into  the  atmosphere,  pi>  =  o  and  pa  —  p*. 
The  fact  that  a  difference  of  pressure  exists  between  two 
points  in  air  transmission  indicates  that  there  are  two  actual 
columns  (or  equivalent  as  in  Fig.  10)  of  air  at  different  den- 
sities connected  and  producing  motion,  or  that  by  mechanical 
means  a  pressure  difference  is  created  which  may  be  re- 
duced to  an  equivalent  head  h  by  dividing  the  pressure  head 
by  the  density  of  the  air.  Thus 

pressure  difference          pa  —  pi> 


density  d 

Let  pa  —  pb  =  px  =  ounces  of  pressure  per  square  inch  of 
area  producing  velocity  of  the  air;  also,  let  g  =  acceleration 
due  to  gravity  =  32.16  and  d  —  density  (weight  of  one  cubic 
foot)  of  dry  air  at  60°  and  at  atmospheric  pressure  (Table 
7,  Appendix).  Substituting  in  the  general  equation 


64.32  X  144p*  

=   87  Vp*  (72) 


.0764  X  16 


250  HEATING  AND  VENTILATION 

Since  the  pressure  producing-  flow  is  usually  measured 
in  inches  of  water,  /*»-,  the  above  may  be  changed  to  read  in 
equivalent  height  of  water  column  by 

weight  of  water  per  cu.  ft.  at  given  temp.   X   /'  <• 

h   =   -  (73) 

weight  of  air  at  given  temperature   X    12 

Applying  this  to  dry  air  at  GO0   and  water  at  the  same  tem- 
perature (Tables  7  and  9,  Appendix,  also  Art.  29), 


12  X  .0764 
which  when  substituted  in  the  general  equation  gives 


v  =  V64.32   X    68  hw   =  66.2  V/i«-  (74) 

Equation  73  between  the  temperatures  of  50°  and  70° 
gives  results  varying  between  v  =  65.5  V/<«  for  50°  and  v  =. 
66.5  V7i«.  for  70°.  Taking  the  average  value 

v  =  66  V^T  (75) 

Stated  as  a  rule  for  approximate  calculations  the  theoretical 
velocity  of  air,  when  measured  by  a  water  column  gage  that  meas- 
ures in  inches  of  water,  equals  sixty -six  times  the  square  root  of  the 
height  of  the  column  in  inches. 

For  calculations  requiring  greater  accuracy,  Equations  72 
and  74  should  take  into  account  the  density  of  the  air  and 
its  drop  in  temperature.  First,  considering  only  density,  let 
the  pressure  of  one  atmosphere  at  sea  level  be  29.92  inches 
of  mercury  (14.7  pounds  =  235  ounces  per  square  inch  area). 
Since  the  density  is  proportional  to  the  absolute  pressure, 
the  temperature  remaining  constant,  we  have  from  Equation 
72  with  air  exhausting  into  the  atmosphere 


/  64.32  X  144  px  I 

=    \  -  —=  1336    \ 

\  9QK    _1_    «_  \ 


235  +  px  235  +  p, 

.0764  X  16  X 


(76) 


235 

Also  from  the  relation  existing  between  Equations  72  and  74, 
Equation  76  reduces  to 


=   1336 

407  +  /» 


PLENUM  WARM  AIR   HEATING 


251 


Second,  considering  both  density  and  temperature,  Equations 
76  and  77  become 


v  =   1336 


460  +  t 


235 


v  —   1336    A  I  — 


(78) 


(79) 


520  /  407  +  hw 
To  facilitate  calculation,  the  second  columns  in  Tables 
XXX  and  XXXI  have  been  compiled  from  Equations  76  and  77 
respectively,  and  the  second  column  in  Table  XXXII  has  been 
compiled  for  different  temperatures  on  the  basis  of  60°  from 
that  portion  of  Equations  78  and  79  included  within  the  paren- 

TABLE  XXX. 

Column  2  figured  from  Equation  76. 


sure  in  ounces 
)er  sq.  in. 

Velocity  of  dry  air  at  60°  es- 
caping  into   the   atmosphere 
through    any   shaped    orifice 
in    any  pipe  or   reservoir  in 
which    a    given    pressure    is 
maintained. 

Vol.    of   air   in 
cu.     ft.     which 
may     be     dis- 
charged    i  n     1 
min.    through 
an   orifice  hav- 
ing an  effective 

H.   P.  required 
to   move  the 
given     vol.     ot 
air    under    the 
given  conditions 
of  discharge. 

01  r* 

area    of    dis- 

(Col. 3  x  Col.  1) 

r\  . 

charge  of  1  sq. 

HH 

Ft.  per  sec.       Ft.  per  min. 

in. 
Col.  3  -7-  144 

16  x  33000 

% 

30.80 

1848.00 

12.83 

0.00044 

% 

43.56 

2613.60 

18.15 

0.00124 

% 

53.27 

3196.20 

22.19 

0.00227 

% 

61.56 

3693.60 

25.65 

0.00349 

% 

68.79 

4127.40 

28.66 

0.00489 

% 

75.35 

4521.00 

31.47 

0.00642 

7/8 

81.37 

4882.20 

33.90 

0.00809  . 

1 

86.97 

5218.20 

36.24 

0.00988 

1% 

92.18 

5530.80 

38.41 

0.01178 

1% 

97.18 

5830.80 

40.49 

0.01380 

1% 

101.90 

6114.00 

42.46 

0.01592 

1% 

106.40 

6384.00 

44.33 

0.01814 

1% 

110.82 

6649.20 

46.11 

0.02046 

1% 

114.86 

6891.60 

47.86 

0.02284 

1% 

118.85 

7131.00 

49.52 

0.02538 

2 

122.47 

7348.20 

51.03 

0.02787 

thesis.  From  these  three  columns  of  tabulations  the  theo- 
retical velocity  of  air  under  any  pressure  and  temperature 
change  may  be  obtained  without  using  the  equations,  by 
multiplying  the  velocities  found  in  Tables.  XXX  and  XXXI 
by  the  factor  for  temperature  correction  given  in  Table 
XXXII.  Other  points  of  information  concerning  velocities, 


252 


HEATING  AND   VENTILATION 


pressures,  weights  and  horse-powers  in  moving  air  may  be 
obtained  by  multiplying  by  the  factors  as  given  in  the  re- 
spective columns. 

TABLE  XXXI. 
Column  2  figured  from  Equation  77. 


Pressure 
head  in 
inches  of 
water 

Velocity  of  dry  air  at  60°  escaping  into   the   atmosphere 
through  any  shaped  orifice  in  any  pipe  or  reservoir  in  which 
a  given  pressure  is  maintained. 

Feet  per  second 

Feet  per  minute 

.1 

20.94 

1256.40 

.2 

29.67 

1780.20 

.3 

36.25 

2175.60 

.4 

41.86 

2511.60 

.5 

46.80 

2708.  Of) 

.6 

51.26 

3075.60 

.7 

55.36 

3321.60 

.8 

59.10 

3546.00 

.9 

62.60 

3756.00 

1. 

66.14 

3968.40 

1.1 

69.36 

4161.60 

1.2 

72.44 

4346.40 

1.3 

75.39 

4523.40 

1.4 

78.21 

4692.60 

1.5 

80.96 

4857.60 

1.6 

83.59 

5015.40 

1.7 

86.16 

5169.60 

1.8 

88.65 

5319.00 

1.9 

91.27 

5476.20 

2. 

93.42 

5605.20 

2.1 

95.72 

5743.20 

2.2 

97.96 

5877.60 

2.3 

100.15 

6009.00 

2.4 

102.29 

6137.40 

2.5 

104.39 

6263.40 

2.6 

106.43 

6385.80 

2.7 

108.46 

6507.60 

2.8 

110.43 

6625.80 

2.9 

112.37 

6742.20 

3. 

114.28 

6856.80 

3.1 

116.15 

6969.00 

3.2 

118.00 

7080.00 

3.3 

119.81 

7188.60 

3.4 

121.60 

7296.00 

3.5 

123.36 

7401.60 

APPLICATION  1. — Air  is  exhausting  from  an  orifice  in  an 
air  duct  into  the  atmosphere.  The  pressure  of  the  air  within 
the  duct  is  one  ounce  by  pressure  gage  or  1.74  inches  of 


PLENUM  WARM  AIR   HEATING 


253 


water  by  Pitot  tube.  Assuming1  the  air  to  be  dry  and  the 
barometer  29.92  inches  when  the  water  in  the  tube  and  the 
air  current  are  60°,  what  is  the  theoretical  velocity  of  the 
air? 

SOLUTION.— By  Tables  XXX  and  XXXI,  r  =  86.97.  Check 
this  by  Equation  76. 

APPLICATION  2. — In  Application  1  let  the  duct  pressure  and 
temperature  be  3  inches  of  water  and  70°  respectively.  What 
is  the  theoretical  orifice  velocity? 

SOLUTION. — From  Table  XXXI,  v  =  114.28  at  60°.  Multi- 
plying this  by  1.01  from  Table  XXXII  =  115.42  F.  P.  S. 
velocity.  Check  by  Equation  79. 

TABLE  XXXII. 


legrees. 

Factor  for  rel- 
ative   vel.    at 
same     pressure 
also     relative 

Factor  for  rel- 
ative   pressure, 
also  wt.  of  air 

Factor  for  rel- 
ative    vel.      to 
move  same  wt. 
of  air  also  rel- 

Factor  for  rel- 
ative power  to 
move  same  wt. 

c 
a 

powers  to  move 
same  vol.  of  air 
at  same  vel.   = 

moved  at  same 
vel.  = 

460"  +  60° 

ative     pressure 
to  produce  the 
vel.    to    move 

of  air  at  vel.  in 
column    4    and 
pressure  in  col- 
umn 4  —  factor 

5 

Vwt,  at  any  T 

T 

same  wt.  of  air 

i  n     column     4 

Wt.  at  460°  +60° 

1  4-  Col.  3 

squared 

30 

.97 

1.07 

.93 

.87 

40 

.98 

1.04 

.96 

.92 

50 

.99 

1.02 

.98 

.96 

50 

.00 

1.00 

1.00 

1.00 

70 

.01 

.98 

1.02 

1.04 

80 

.02 

.96 

1.04 

1.08 

90 

.03 

.94 

1.06 

1.13 

100 

.04 

.92 

1.09 

1.19 

125 

.06 

.89 

1.12 

1.25 

150 

.08 

.85 

1.18 

1.39 

175 

.10 

.82 

1.22 

1.49 

200 

.13 

.79 

-  1.27 

1.61 

250 

.17 

.73 

1.37 

1.88 

300 

.21 

.68 

1.47       • 

2.16 

350 

.25 

.64 

1.56 

2.43 

400 

.28 

.60 

1.67 

2.79 

500 

.36 

.54 

1.85 

3.42 

600 

.43 

.49 

2.04 

4.16 

700 

.49 

.45 

2.22 

•   4.93 

800 

.56 

.41 

2^44 

5.95 

145.  Actual  Amount  of  Air  Exhausted: — When  air  at 
any  pressure  is  exhausted  from  one  receptacle  to  another 
through  an  orifice,  nozzle  or  short  pipe,  the  actual  velocity 
is  reduced  below  the  theoretical  velocity  and  the  effective 


254 


HEATING  AND   VENTILATION 


area  of  the  jet  or  stream  is  less  than  the  actual  area  of  the 
opening.,  These  variations  are  due  to  the  shape  of  the  inlet 
and  the  friction  on  the  contact  surface.  To  find  the  amount 
of  air  Q  moved  per  second,  multiply  the  theoretical  velocity 
by  the  actual  area  and  by  a'  constant  which  is  the  product 
of  the  coefficient  of  reduced  velocity  and  the  coefficient  of 
reduced  area.  Q  =  (' r  A,  where  ('  =  constant,  usually  called 
coefficient  of  efflux.  Kent,  page  615,  quotes  from  experiments 
by  Weisbach  the  following-  values: 
For  conoidal  mouthpiece,  of  form  of  the 

contracted     vein,     with     pressures     of 

from   0.23   to   1.1   atmospheres C 


0.97  to  0.99 
0.56  to  0.79 
0.81  to  0.84 


Circular  orifice  in  thin  plate C   = 

Short  cylindrical  mouthpiece  C   — 

Short  cyl.  mouthpiece  rounded  at  the  inner 

end    c   =    0.92  to  0.93 

Conical  converging  mouthpiece  C   =    0.90  to  0.99 

146.  Results  of  Tests  to  Determine  the  Relation  be- 
tween Pressure  and  Velocity  in  Air  Transmission: — In  fan 
construction  the  number  and  shape  of  the  blades,  the  sizes 
of  the  inlet  and  outlet  openings,  the  shape  and  size  of  the 
casement  around  the  wheel  and  the  speed,  all  have  an  effect 
upon  the  relation  between  the  pressure  and  the  velocity  of 
the  air  discharge.  From  tests  conducted  by  the  author,  the 
curves  shown  in  Fig.  148  were  obtained.  A  No.  2  Sirocco 


.2-3         4         .5 
RATIO  OF  OPENING 
Fig.   148. 


8         .9 


0 


PLENUM  WARM  AIR   HEATING  255 

blower  was  belted  to  an  electric  motor  and  delivered  air  to 
a  horizontal,  circular  pipe  whose  length  was  nine  times  the 
diameter.  This  pipe  was  provided  with  reducing-  nozzles 
which  varied  the  area  of  discharge  by  tenths  from  full  open- 
ing to  full  closed.  The  air  tube  was  provided  also  with 
manometer  tubes  for  static,  dynamic  and  velocity  pressures, 
also,  an  adjustable  scale  reading  in  two  positions,  either  .01 
or  .002  inch  of  water.  The  gross  power  was  taken  by  watt- 
meter and  the  delivered  power  from  motor  to  fan  was  taken 
by  dynamometer.  In  addition  to  this,  the  frictional  horse- 
power of  the  fan  and  motor  unit  was  obtained  by  removing 
the  fan  wheel  from  the  shaft  and  taking  readings  with  all 
other  conditions  remaining  as  nearly  constant  as  possible. 
The  frictional  power,  when  deducted  from  the  gross  power 
recorded  by  the  wattmeter,  gave  the  readings  for  the  net 
horse-power  curve.  A  galvanized  iron  intake,  enlarged  from 
the  size  of  the  fan  intake  to  a  rectangular  four  square  feet 
in  area  and  divided  by  fine  wires  into  squares  to  the  size  of 
the  standard  anemometer,  was  used  to  find  the  volume  of  air 
moved  per  minute.  This  volume  is  shown  in  the  curve 
C.  F.  M.  To  check  the  curve,  the  volume  was  calculated  for 
each  opening  by  the  Pitot  tubes  on  the  side  of  the  experi- 
mental pipe. 

To  fully  understand,  this  article,  refer  to  Art.  29  and  note 
that  A,  Fig.  12,  registers  static  pressure  plus  velocity  pressure. 
This  sum  may  be  called  the  dynamic  pressure.  Also  note  that 
B  registers  only  static  pressure,  i.  e.,  that  pressure  which  acts 
equally  in  all  directions  and  serves  no  usefulness  in  moving 
the  air.  Also,  note  that  A  —  Ji  =  C,  i.  e.,  dynamic  pressure 
minus  static  pressure  equals  velocity  pressure.  When  ap- 
plied in  th'e  form  shown  by  C,  the  pressure  recorded  is  that 
due  to  the  velocity  only.  This  is  the  form  commonly  used. 
Referring  again  to  Fig.  148,  A  V  P  is  that  pressure  recorded 
by  C  when  applied  to  the  air  current  at  the  fan  outlet,  =  air 
velocity  pressure.  P  V  P  is  that  pressure  (obtained  by  Equa- 
tions 72  and  77)  that  would  be  shown  on  C  if  the  air  were 
moving  as  fast  as  the  tip  of  the  blades  on  the  fan  wheel,  = 
peripheral  velocity  pressure.  P  V  P  =  1  in  Fig.  148.  D  P 
is  the  dynamic  pressure  and  would  be  found  by  applying  A 
only.  S  P  is  the  static  pressure  as  stated  above. 

In  the  tests,  the  fan  was  run  at  constant  speed  and  the 
dynamic,  static  and  velocity  pressures  were  measured  about 


256 


HEATING  AND   VENTILATION 


midway  of  the  pipe  at  full  opening.  Then  the  openings  were 
changed  by  10  per  cent,  reductions  until  the  pipe  was  fully 
closed  and  similar  readings  taken  for  each  reduction.  These 
readings  were  plotted  in  the  upper  set  of  curves.  Because 
the  manometer  tubes  were  located  some  distance  from  the 
end  of  the  experimental  pipe,  there  was  a  static  pressure, 
al),  recorded  at  full  opening.  This  caused  the  dynamic  pres- 
sure to  be  raised  a  corresponding  amount,  a'  b'.  If  the  tubes 
had  been  located  at  the  delivery  end  of  the  pipe  the  static 
and  dynamic  pressures  would  have  fallen  from  6  and  1)'  to 
({•  and  a'.  The  peripheral  velocity  of  the  wheel  was  2828  feet 
per  minute  and  the  corresponding  pressure,  with  corrections 
for  temperature,  was  found  by  Equation  75  to  be  .5  inch  of 


IP 


* 


2         .3         4         5 
RATIO  OF  OPENING 
Fig.  149. 

water.  The  relation  between  the  peripheral  velocity  pres- 
sure and  the  air  velocity  pressure  is  shown  in  the  upper 
curve,  Fig.  149.  In  applying  this  to  fan  practice  it  shows 
the  relation  between  the  velocity  of  a  point  on  the  wheel 
circumference  and  that  of  the  air  leaving  the  wheel.  Notice 
that  at  full  opening  and  discharging  into  free  air, 
AVP  :  PVP  ::  1.2  :  1.  Since  the  velocities  vary  as  the 
square  roots  of  the  pressures  (r  —  \/2y//),  we  find  the  veloc- 
ities to  be  VI. 20  :  VI  =  1.1  :  1.  That  is  to  say,  for  this  fan 
the  air  velocity  at  the  free  opening  of  the  fan  is  1.1  times 


PLENUM  WARM  AIR   HEATING  257 

the  peripheral  velocity  of  the  wheel.  The  corresponding- 
velocity  of  air  from  a  steel  plate  fan  as  reported  by  the 
American  Blower  Co.  and  as  shown  on  the  lower  chart,  is 
V~4lf  :  Vl~~=  .67  :  1,  or  .61  of  the  speed  of  the  Sirocco  fan 
for  the  same  wheel  speed.  The  resistance  offered  by  the 
ducts  in  the  average  plenum  heating  system  is  equivalent, 
we  will  say,  to  that  offered  by  a  75  per  cent,  gate  opening  in 
the  experimental  pipe.  According  to  the  diagrams  for  this 
opening,  the  ratio  AVP  to  PVP  is  1.04  for  the  Sirocco  fan 
and  .25  for  the  steel  plate  fan.  The  ratio  of  the  air  velocities 
to  the  peripheral  velocities  then  are,  respectively,  VI. 04  : 
Vl~=  1.02  :  1  and  V.~25~ :  \/T~=  .5  :  1.  These  show  that  with 
a  75  per  cent,  opening  and  with  the  fan  wheels  running  with 
a  peripheral  velocity  of  3000  feet  per  minute,  the  air  would 
be  entering  the  ducts  at  1.02  X  3000  =  3060,  and  .5  X  3000  = 
1500  feet  per  minute  respectively  for  the  two  types.  Con- 
versely, if  it  were  desired  to  have  the  air  enter  the  ducts  at 
1500  feet  per  minute,  with  a  resistance  equivalent  to  a  75 
per  cent,  opening,  the  fan  wheels  would  have  peripheral 
speeds  of  1500  -=-  1.02  =  1470,  and  1500  •*-..&=  3000  feet  per 
minute  respectively.  From  these  velocities  may  be  obtained 
the  wheel  diameter  for  any  given  R.  P.  M.  Other  models  of 
the  Sirocco  and  multiple  blade  type  of  fans  will  show  dif- 
ferent characteristics  than  the  one  under  consideration.  It 
will  be  seen  from  the  above  analysis  that  the  change  in  con- 
struction from  the  steel  plate  type  to  the  multiblade  type 
permits  a  smaller  wheel  and  fan  to  be  installed  for  any  given 
work  desirable.  From  Equation  86  it  is  seen  that  the  power 
required  to  drive  a  fan  varies  as  the  fifth  power  of  the 
diameter  and  as  the  cube  of  the  speed.  With  a  given  amount 
of  air,  Q,  required  per  minute,  the  power  will  be  diminished 
by  reducing  the  diameter  of  the  wheel  or  by  reducing  the 
speed  of  the  fan.  Manufacturers'  catalogs  should  be  con- 
sulted for  capacities,  sizes,  etc.  Such  tables  are  supplied  by 
the  trade  in  form  for  easy  reference  and  use. 

147.  Work  Performed  and  Horse-Power  Consumed  in 
Moving:  Air: — The  foot  pounds  of  work  performed  in  moving 
air  equals  the  product  of  the  moving  force  into  the  distance 
moved  through  in  any  given  time.  Let  pa  —  pb  =  px  =  mov- 
ing force  of  air  in  ounces  per  square  inch  and  A  =  cross- 
sectional  area  of  air  stream  in  square  inches.  Then  the 


258  HEATING  AND  VENTILATION 

pounds  per  square  inch  will  be  p*  -^  16,  and  the  foot  pounds 
of  .work,  W,  and  the  horse-power,  H.  P.,  absorbed  per  minute 
by  the  air  will  be 

60  j)x  A  v 

W  =  —       =  2.75pxAv  (80) 

16 

3.75  px  A  v 

H.  P.  =  -  -  =  .OOOlHp*  Av  (81) 

33000 

Equation  81  may  be  stated  in  terms  of  the  cubic  feet  or  air 
discharged  per  minute.  Take  the  relation  between  px  and  hw 
at  60°  as  12  px  =  16  X  .433  /**•;  also  the  relation  Av  =  144  g 
when  Q  =  cubic  feet  of  air  discharged  per  second  and,  from 
Equation  75,  7/,t-  =  r-  -:-  4356.  Then  by  substituting  in  Equa- 
tion 81 

3.75  X  .577  X  f2  X  144  Q 

H.  P.  = =   .0000022  vs  Q        (82) 

4356  X  33000 

In  Equations  80  to  82,  pr  —  total  pressure  drop  in  system  be- 
ing investigated  (dynamic  pressure),  and  v  =  velocity  cor- 
responding to  pi. 

ILLUSTRATION. — In  a  plenum  heating  and  ventilating  sys- 
tem the  pressure  above  atmosphere  at  the  fan  outlet  (gage 
pressure,  corresponding  to  resistance  of  ducts  and  heater 
coils)  is  .6  inch  of  water;  the  pressure  below  atmosphere  at 
the  fan  inlet  (resistance  of  tempering  coils  and  air  inlet)  is 
.15  inch  of  water;  the  equivalent  velocity  head  is  .25  inch  of 
water;  then  the  pressure  the  fan  is  working  against  is  1  inch 
of  water  =  .58  ounce  —  pr. 

APPLICATION  1. — The  constant  area  of  a  stream  of  dry  air 
at  60°  exhausting  between  the  pressures  of  pa  =  1%  ounces 
and  pb  =  V2  ounce,  is  400  square  inches.  What  is  the  work 
performed  per  minute  and  the  horse-power  consumed?  (For 
velocity  see  second  column  Table  XXX), 

W  =  3.75  X  (1%  —  %)  X  400  X  86.97  =  130500  foot 
pounds,  and  //.  P.  =  .000114  X  (1%  —  %)  X  400  X  86.97  = 
3.96. 

APPLICATION  2. — A  fan  is  delivering  1000000  cubic  feet  of 
air  per  hour  to  a  heating  system  at  a  temperature  of  100° 
and  with  a  total  pressure  of  %  ounce.  What  is  the  theoret- 
ical horse-power  of  the  fan?  From  Tables  XXX  and  XXXII, 
v  =  75.35  X  1.04  =  78.36  and 

//.  P.   =   .0000022   X    (78.36)2   X    278  =   3.76 


PLENUM   WARM  AIR   HEATING  259 

The  actual  horse-power  of  a  blower  fan  is  the  horse-power 
absorbed  in  moving1  the  air  plus  the  horse-power  absorbed 
by  the  blower.  Let  E  =  efficiency  of  the  blower.  Then  Equa- 
tions 81  and  82  become 

. 000114  px  A  v 

H.  P.  =  -  (83) 

B 

. 0000022  V2Q 

H.  P.   =  (84) 

E 

The  value  of  E  changes  with  the  type  of  fan.  In  the 
steel  plate  fan  it  will  vary  from  20  to  40  per  cent.  Average 
30  per  cent.  In  the  Sirocco  and  multiblade  fans  it  will  vary 
from  50  per  cent,  at  50  per  cent,  rated  capacity  to  70  per  cent, 
at  100  per  cent,  rated  capacity.  The  latter  value  is  safe 
(See  also  Art.  152). 

148.      Carpenter's   Practical   Rules   for   Fan   Capacities: — 

Professor  Carpenter  in  H.  &  V.  B.  has  summarized  tests  on 
steel  plate  fans  as  follows: 

Rule. — "The  capacity  of  fans,  expressed  in  cubic  feet  of  air  de- 
livered per  minute,  is  equal  to  the  cube  of  the  diameter  of  the  fan 
ivheel  in  feet  multiplied  by  the  number  of  revolutions  multiplied  by 
a  coefficient  'having  the  following  approximate  value  :  for  fan  with 
single  inlet  delivering  air  without  pressure,  0.6  ;  delivering  air  with 
pressure  of  one  inch,  0.5  ;  delivering  air  with  pressure  of  one  ounce, 
0.4  ;  for  fans  with  double  inlets,  the  coefficient  should  be  increased 
about  50  per  cent.  For  practical  purposes  of  ventilation,  the  ca- 
pacity of  a  fan  in  cubic  feet  per  revolution1  will  equal  .4  the  cube 
of  the  diameter  in  feet." 

Rule. — "The  delivered  horse-power  required  for  a  given  fan  or 
blower  is  equal  to  the  5th  power  of  the  diameter  in  feet,  multiplied 
by  the  cube  of  the  number  of  revolutions  per  second,  divided  by  one 
million  and  multiplied  by  one  of  the  following  coefficients  :  for  free 
delivery,  30 ;  for  delivery  against  one  ounce  pressure,  20  ;  for  de- 
livery against  two  ounces  of  pressure,  10." 

Stated  as  equations  these  rules  are  as  follows: 


Cu.  ft.  of  air  per  min. 

(85) 
C  X  RPM 

where  D   =z   the  diameter  in  feet  and  C   =   the  coefficient,  .4 


260 


HEATING  AND   VENTILATION 


for  pressure  of  one  ounce,  .5   for  pressure  of  one  inch,  and 
.6  for  no  pressure. 


//.  P.  = 


(R 


X  C 


1000000 


(86) 


where  C  =  30  for  open  flow,  20  for  one  ounce  and  10  for  two 
ounces  pressure  respectively. 

Note. — In  using-  Equations  85  and  86  for  Sirocco  or  multi- 
vane  fans,  C  should  be  1.1,  1.2  and  1.3  for  85,  and  100,  95 
and  90  for  86. 

149.  Approximate  Fan  Size*: — Table  XXXIII  gives  sizes 
of  important  features  in  fan  casing,  wheel  and  openings  re- 
ferred to  the  wheel  diameter. 


TABLE  XXXIII. 


Diameter  of  wheel  

Diameter  of  inlet,  single 

Dimensions  of  exhaust 

Wheel  width  inlet  circum... 
Wheel  width  outer  circum... 


Steel  plate  fan     Multiblade  fan 


D 

.60   D  to  .70    D 

.50    D  to  !60   D 

.50   D  to  .60   D 

.35    D  to  .45    D 


1.0  D  to  1.2  D 

.6  D  to     .8  D 

by  .7  D  to  1.0  D 

.5  D 


Type  of  fan 

Space 
occupied 
Full  housed 

Discharge 
vert. 

Discharge 
horiz. 

Steel  plate  

1.7  D  to  1.5  D 

1.5  D  to  1.7  D 

Multiblade   

Length 

1.8  D  to  2.0  D 

1.4  D  to  1.6  D 

Steel  plate  
Multiblade   

Height 

1.5  D  to  1.7  D 
1.4  D  to  1,6  D 

1.7  D  to  1.5  D 
1.8  D  to  2.0  D 

Steel  plate  
Multiblade   

Width 

.7  D  to  1.2  D 
1.3  D  to  1.5  D 

.7  D  to  1.2  D 
1.3  D  to  1.5  D 

PLENUM  WARM  AIR   HEATING 


261 


150.  Selection  of  Fan  for  Given  Capacity: — By  calculation. 
—  (See  Art.  153,  Application  1). 

By  graphical  analysis. — Assume  the  conditions  given  in  Art. 
153,  Application  1,  and  apply  Fig.  150  as  follows:  locate  33330 
on  the  C  F  M  scale,  rise  vertically  from  this  point  to  the  in- 


EXAMPLB     SHOWING    APPLICA- 
TION OF  CURVES. 

PROBLEM.  Determine  size  of 
fan,  revolutions  per  minute  and 
brake  horse-power  required  to  de- 
liver 80,000  cubic  feet  per  minute 
against  a  static  pressure  of,  2.5" 
W.  G. 

SOLUTION.  —  Locate  80,000  on 
the  C.  F.  M.  scale  and  project  ver- 
tically upward  from  this  point  to 
the  intersection  of  that  fan  work- 


ing nearest  50%  ratio  opening  at 
2.5"  S.  P.,  which  in  this  case  is 
Fan  No.  13  (follow  dash  lines  on 
curves) .  From  this  point  project 
horizontally  to  intersect  2.5"  S.  P. 
curve  and  from  thence  upward 
parallel  to  horse-power  lines  to  in- 
tersect Fan  No.  13  at  which  point 
read  53.5  B.  H.  P.  on  horse-power 
scale  to  left.  From  same  point  on 
P.  curve  project  vertically 
downward  to  intersect  Fan  No.  13 
reading  218  R.  P.  M.  on  scale  to 
left. 

Fig".   150. 

tersection  of  that  fan  working  nearest  50  per  cent,  ratio 
opening  at  1  inch  static  pressure  and  find  a  No.  10  fan.  Move 
horizontally  to  the  left  past  the  outlet  velocity  1700  to  the 
intersection  with  the  1  inch  static  pressure  curve.  Call  this 


262  HEATING  AND  VENTILATION 

point  A.  From  here  drop  vertically  past  the  peripheral 
velocity  2850  feet  per  minute  to  the  No.  10  slope  and  then 
move  horizontally  to  the  left  to  180  revolutions  per  minute. 
Also,  from  A  parallel  the  horse-power  curve  to  the  end,  then 
rise  to  curve  No.  10  and  move  horizontally  to  the  left  to  9 
horse-power.  Check  the  peripheral  and  outlet  velocities, 
also  other  values  found,  by  Table  57,  Appendix. 

Similar  charts  of  workable  size  may  be  had  from  the  manufac- 
turers covering  fans,  Nos.  9  to  16  inclusive. 

151.  Fan  Drivest — Fans  for  heating  and  ventilating  pur- 
poses may  be  driven  by  simple  horizontal  or  vertical,  throt- 
tling or  automatic  steam  engines,  or  by  electric  motors.  In 
either  engine  or  motor  drives  the  power  may  be  direct-con- 
nected or  belt-connected  to  the  fan.  Direct-connected  fan 
units  make  very  neat  arrangements  but  they  require  slow 
speed  engines  or  motors  and  are  frequently  so  large  as  to 
be  prohibitive.  Engine  fans  having  poor  attention  are  liable 
to  pound,  the  noise  carrying  through  the  fan  to  the  air  cur- 
rent and  up  to  the  rooms.  In  belted  drives  engines  or  mo- 
tors are  run  at  higher  speeds  and  are  either  set  off  from  the 
fan  10  feet  or  more  to  get  good  belt  contact  or  used  with  a 
tightener.  Chain  drives  are  sometimes  installed.  They  are 
positive  in  speed,  fairly  quiet  in  operation,  permit  the  same 
speed  reductions  as  belt  drives  and  economize  floor  space. 

In  deciding  between  engine  or  motor  drives  with  steam 
coils,  the  steam  from  the  engine  should  be  considered  a 
credit  to  the  heating  system  since  it  is  exhausted  into  the 
heater  coils  and  used  instead  of  live  steam  from  the  boilers. 
Engines  of  high  efficiency  are  not  essential  when  the  ex- 
haust steam  can  be  used  for  heating.  Enclosed  engines  run- 
ning in  oil  are  preferred  for  high  speeds.  Belt  drives  should 
have  the  tight  side  below  to  increase  the  arc  of  contact. 

Electric  motors  should  be  specified  for  installations 
where  exhaust  steam  can  not  be  used,  as  in  systems  for 
ventilating  only.  They  are  more  satisfactory  in  many  ways 
than  steam  engines  but  are  more  expensive  to  operate. 
Direct  current  motors  are  desired  in  many  places  because 
of  the  convenience  in  obtaining  speed  changes  and  direct- 
connections.  Alternating  current  motors  operate  at  higher 
speeds,  but  may  have  speed  reductions  of  40  per  cent,  where 
required.  When  motors  are  specified  the  alternating  current 
constant  speed  machine  with  belt  drive  is  generally  selected. 


PLENUM  WARM  AIR  HEATING 


263 


152.  Speed  of  the  Fan: — A  blower  fan,  exhausting  into 
the  open  air,  will  deliver  air  with  a  lineal  velocity  approx- 
imately that  of  the  peripheral  velocity  of  the  fan  blades.  If 
this  same  fan  is  connected  to  a  system  of  ducts  and  heater 
coils,  the  lineal  velocity  of  the  air  is  reduced  because  of  the 
increased  resistance  in  the  duct  system.  This  causes  the  air 
to  lag  or  slip  between  the  fan  blades  and  the  casing-.  In  the 
average  heating  system  using  multiblade  fans  this  slip  may 
be  as  great  as  30  per  cent.  (See  Art.  146).  It  is  sometimes 
convenient  in  applying  blowers  to  heating  systems  to  con- 
sider the  lineal  velocity  of  the  air  as  it  leaves  the  fan  to  be 
two-thirds  that  of  the  periphery  of  the  fan  blades.  Since 
the  velocity  of  the  air  upon  delivery  from  the  fan  should  not 
exceed  1800  to  2500  feet  per  minute,  the  outer  point  on  the 
fan  blades  should  not  be  expected  to  move  faster  than  2700 
to  3750  feet  per  minute.  Knowing  this  peripheral  velocity, 
the  revolutions  per  minute  may  be  selected  and  the  diameter 
obtained. 

In  direct-connected  fans  the  revolutions  per  minute  must 
agree  with  those  of  the  attached  engine  or  motor.  In  belted 
fans  this  restriction  does  not  apply.  Ordinary  blower  fans 
running  at  high  speeds  are  noisy  and  practice  has  deter- 
mined the  number  of  revolutions  to  use.  Table  XXXIV  gives 
speeds  that  may  be  recommended  for  such  use. 

TABLE  XXXIV. 
Speeds  of  Sirocco  and  Multiblade  Blower  Fans,  in  R  P  M 


Differential  pressures 

of  wheel 

.288  oz. 

.433  oz. 

.577  oz. 

.865  oz. 

1.154  oz. 

in  inches 

.5  in. 

.75  in. 

lin. 

1.5  in. 

2  in. 

24 

322 

S91 

454 

554 

642 

.36 

214 

260 

302 

369 

427 

48 

161 

196 

225 

277 

321 

60 

129 

157 

181 

223 

257 

72 

107 

130 

151 

185 

214 

84 

92 

112 

130 

159 

184 

90 

86 

104 

121 

148 

171 

96 

81 

99 

113 

139 

160 

In  recent  developments  in  blower  fans  the  number  of 
blades  has  been  increased  and  the  depth  of  the  blades  has 
been  diminished,  making  the  operation  of  the  fan  somewhat 
similar  to  that  of  the  steam  turbine.  These  changes  have 


264  HEATING  AND  VENTILATION 

produced  higher  efficiencies  under  test  than  were  possible 
with  the  ordinary  steel  plate  or  paddle  wheel  fan.  As  a  re- 
sult, fan  sizes  for  given  capacities  have  been  reduced. 
Tables  55,  56  and  57,  Appendix,  give  summaries  of  the  latest 
catalog  data. 

153.  Selection  of  the  Engine  and  Fan: — Determine  the 
power  of  the  fan  from  Equations  83  or  84.  Assume  a  certain 
ratio  between  this  and  the  engine  power,  say  as  3  is  to  4, 
then 

4 

H.  P.  of  the  engine  =  —  77.  P.  of  the  fan  (87) 

3 

Having  obtained  the  horse-power  of  the  engine,  find  the 
size  of  the  cylinder  as  follows:  let  />«  =  absolute  initial 
pressure  of  the  steam  in  the  cylinder,  and  r  =  number  of 
the  steam  expansions  in  the  cylinder  =:  reciprocal  of  the  per 
cent,  of  cut-off  =  the  sum  of  the  displacement  at  release 
plus  the  clearance  divided  by  the  sum  of  the  displacement 
at  cut-off  plus  the  clearance.  The  cut-off  allowed  for  high 
speed  engines  in  power  service  approximates  25  per  cent, 
stroke,  but  in  engines  for  blower  work  this  may  be  taken 
50  per  cent,  stroke.  Find  the  mean  effective  pressure,  pit  by 
the  equation 

1   +  hyperbolic  logarithm  of  r 

j)l  =  pn  —  —  back  pressure   (88) 

r 

Let  I  =  length  of  the  stroke  in  inches  and  2V  =  number  of 
revolutions  per  minute  and  apply  the  equation 

2pi  I  AN 

77.  P.  =  (89) 

12  X  33000 

and  find  A,  the  area  of  the  cylinder,  from  which  obtain  d, 
the  diameter  of  the  cylinder.  In  applying  Equation  89  it 
will  be  necessary  to  assume  1.  For  engines  operating  blow- 
ers this  may  be  taken 

2  I  N  —  200  to  400 

Equation  88  assumes  that  the  steam  in  the  cylinder  ex- 
pands according  to  the  hyperbolic  curve,  p  v  =  p'  v'.  For 
values  of  hyperbolic  (Naperian)  logarithms  see  Table  5, 
Appendix.  It  also  assumes  no  loss  in  the  recompression  of 
the  steam  in  the  cylinder.  Both  assumptions  are  only  ap- 
proximately correct,  but  the  errors  are  slight  and  to  a  cer- 
tain degree,  tend  to  neutralize  each  other,  hence  the  final 


t 

PLENUM  WARM   AIR  HEATING  265 

results  from  this  equation  are  near  enough  to  be  used  for 
fan  engine  calculations.  For  such  work  as  this,  r  may  be 
taken  from  2  to  3.  The  back  pressure  should  not  be  higher 
than  5  pounds  gage  (19.7  pounds  absolute).  This  is  deter- 
mined by  the  pressure  in  the  coils  carrying  exhaust  steam, 
which  frequently  drops  to  atmosphere  or  below. 

In  determining  the  cylinder  diameter  and  length  of 
stroke  it  may  be  necessary  to  make  two  or  more  trial  appli- 
cations before  good  sizes  are  obtained.  When  initial  steam 
pressures  are  low,  say  not  to  exceed  30  pounds  gage,  mean 
effective  pressures  are  small,  thus  requiring  cylinders  of 
large  diameter.  In  such  cases  the  diameter  of  the  cylinder 
may  be  greater  than  the  length  of  stroke.  Where  high 
pressure  steam  is  used,  say  100  pounds  gage,  the  diameter 
of  the  cylinder  will  be  less  than  the  length  of  the  stroke. 

APPLICATION  1. — Assume  the  following  to  fit  the  design 
shown  in  Figs.  151,  152  and  153;  dry  steam  to  the  engine  at 
100  pounds  gage  pressure;  direct-connected  unit;  Sirocco 
type  fan,  single  inlet,  00  per  cent,  efficiency,  running  at  180 
revolutions  per  minute  and  delivering  2000000  cubic  feet  of 
air  per  hour  to  the  building  against  a  static  pressure  of  1 
inch  of  water  (total  pressure  1.15  inch).  (See  Table  57,  Ap- 
pendix); steam  cut-off  in  the  cylinder  at  one-third  stroke 
and  used  in  the  coils  at  5  pounds  gage  pressure.  Find  the 
sizes  and  horse-powers  of  the  engine  fan  unit. 

From  Equation  84,  with  v  =  velocity  due  to  a  total  pres- 
sure of  1.15  inch  of  water, 

.0000022  X   (71)2  X  555.5 

Fan  H.  P.  =  -  -  =   10.26 

.60 

From  extended  tables  of  the  A.  B.  Co.  similar  to  Table  57, 
Appendix,  find  a  No.  10  fan,  60  inch  wheel,  33650  C.  F.  M.,  181 
R.  P.  M.,  10.2  H.  P.  Peripheral  velocity  of  wheel  2845  F.  P.  M. 
Checking  these  values  with  Equations  85  and  86 


a    /  2000000 

D  of  fan  =     .*    —  5.2  ft.  =  62  in. 

*     60  X  1.3  X  180 

(5.2)5  X   (3)3  X  97 

H.  P.  of  fan  =  —  -  =  10.1 

1000000 

From  Equations  87,  88  and  89. 

4 

H.  P.  of  engine  =  —  X   10.26   =  13.68 
3 


266  HEATING  AND  VENTILATION 

/  1  +  1.0986    \ 
Pi  =  115       I  J  —  19.9  =  60.5  Ibs.  per  sq.  in. 

If   2    I  N    =    250,    I    =    250    4-    360    =    .69    ft.    =    8.25    in.    and 

13.68  X  12  X  33000 

A  =  =   30  sq.   in.   =    6.25  in.  diameter. 

2  X  60.5  X  8.25  X  180 

The  engine  is  6.25  in.   X   8.25  in.,  at  180  R.  P.  M. 

APPLICATION  2. — Assume  the  values  as  in  Application  1, 
excepting  that  the  steam  is  taken  from  a  conduit  main  at 
a  pressure  of  30  pounds  per  square  inch  gage,  that  2  I  N  — 
300,  and  that  the  steam  cut  off  in  the  cylinder  is  at  one-half 
stroke.  As  before,  D  of  fan  =  5.2  ft.;  H.  P.  of  fan  =  10.26; 
and  H.  P.  of  engine  —  13.68.  The  mean  effective  pressure  is 

(1  +  .6931    \ 
I  —  19.9   =   18.2  Ibs.  per  sq.  in. 
2  / 

13.68  X  12  X  33000 

A   =  —    83  sq.  in.,  and  the  size  of 

2  X  18.2  X  10  X  180 

the  engine  is  10.25  in.   X   10  in.,  at  180  R.  P.  M. 

154.      Piping   Connections   Around   Heater   and   Engine: — 

Where  fans  are  run  by  steam  power  the  steam  supply  pres- 
sure is  higher  than  that  in  the  coils  and  the  live  steam  must 
enter  the  coils  through  a  pressure  reducing  valve.  Where 
this  reduction  is  made  to  5  pounds  or  below,  the  live  steam 
may  enter  the  same  main  with  exhaust  steam  from  the  en- 
gine, the  back  pressure  valve  on  the  exhaust  steam  line  pro- 
viding an  outlet  to  the  atmosphere  in  case  the  pressure  runs 
above  the  5  pounds  allowable  back  pressure.  If  the  back 
pressure  increases  above  5  pounds,  the  efficiency  of  the  en- 
gine is  reduced.  Where  the  condensation  from  the  live 
steam  is  desired  free  from  oil,  a  certain  number  of  coils  are 
tapped  for  exhaust  steam  and  this  condensation  trapped  to 
a  waste  or  sewer,  the  other  coils  delivering  to  a  receiver  for 
boiler  feed  or  other  purposes  as  may  be  required. 

Every  heating  system  should  be  fully  equipped  with 
pressure  reducing  valves,  back  pressure  valves,  traps,  and  a 
sufficient  number  of  globe  or  gate  valves  on  the  steam  sup- 
ply and  gate  valves  on  the  returns  to  make  the  system 
flexible  and  responsive  to  varying  demands.  Supply  and  re- 
turn connections  for  heater  stacks  should  be  the  same  as  for 
the  amount  of  direct  radiation  that  will  condense  the  same 


PLENUM  WARM  AIR   HEATING 


26' 


amount  of  steam.  Some  engineers  advocate  a  water-seal  of 
20  to  30  inches  on  the  return  end  of  each  section,  thus  mak- 
ing- each  section  independent  in  its  action.  Where  the  coils 
are  very  deep  this  is  a  benefit. 

155.  Application  to  School  Buildings: — Figs.  151,  152  and 
153,  and  Table  XXXV  show  an  application  of  plenum  heat- 
ing and  ventilating  to  a  school  building.  The  table  gives 
some  of  the  calculated  results.  Most  of  the  applications 
throughout  Chapters  X,  XI  and  XII,  also  refer  to  this  same 
building. 

The  plans  show  the  double  duct  system  with  plenum 
chamber  and  ducts  laid  just  below  the  basement  floor.  The 
small  arrows  show  the  heat  registers  and  vent  registers  for 
each  room.  The  same  stack  which  serves  as  a  heat  car- 
rier to  the  room  on  one  floor  serves  as  the  vent  stack  for 
the  corresponding  room  on  the  floor  above,  there  being  a 
horizontal  cut-off  between  them.  The  cut-off  at  the  heat 
register  is  curved  to  throw  the  current  of  heated  air  into  the 
the  room  with  the  least  possible  friction  or  eddy  currents. 

TABLE  XXXV. 
Data  Sheet  for  Figs.  151,  152,  153. 


Room 

Heat  loss 
in  B.  t.  u. 
per  hour  from 
room,  not 
counting 
ventilation 

Room 

Heat  loss 
in  B.  t.  u. 
per  hour  from 
room,  not 
counting1 
ventilation 

Room 

Heat  loss 
in  B.  t.  u. 
per  hour  from 
room,  not 
counting 
ventilation 

1 

2 

3 
4 
5 
6 

7 

51,520 
74,200 
29,400 
36,260 
42,210 
35,350 

11 
12 
13 
14 
15 
16 
17 

81,130 
126,973 
44,583  • 
60,907 
70,224 
50,862 
51,940 

21 

22 
23 
24 
25 
26 
27 

81,130 
17,150 
113,800 
17,150 
35,189 
53,438 
102,333 

8 
9 
10 

16,520 
16,520 
42,210 

18 
19 
20 

24,843 
23,660 
63,840 

28 
29 
30 

28,420 
37,380 
54,110 

Totals 

344,190 

Totals 

540,100 

Totals 

598,961 

268 


HEATING  AND   VENTILATION 


PLENUM  WARM  AIR   HEATING 


269 


CO 

5§ 


s  § 


Jsd_J=ra'ol=dJ=4   1=1 


t5     *£ 


••) 


\: 


Fig.  152. 


270 


HEATING  AND  VENTILATION 


ss 


pS8|   »' 

Sv  [_  JP  O 


-1  tt, 
O  Q 


71 


\     / 


L 


/  \ 


Fig.  153. 


PLENUM  WARM  AIR  HEATING  271 

156.      Application   of   Split    System   to   School   Building: — 

Figs.  154,  155  and  156  show  the  plans  of  a  school  building 
heated  by  direct-radiation  and  ventilated  by  fan-coil  system. 
These  are  included  especially  to  show  the  arrangements  of 
the  ducts  and  indirect  apparatus  on  the  basement  plan. 
Some  of  the  principal  points  in  the  design  of  the  indirect 
section  of  this  plant  are  as  follows:  Air  moved  by  the  fan 
per  minute,  30000  cu.  ft.  against  a  static  pressure  of  %  in. 
of  water;  fan,  at  a  tip  speed  of  2700  f.  p.  m.,  requires  9  horse- 
power; motor  horse-power,  12;  50"  vento  coils,  3  stacks  deep, 
5"  centers,  arranged  in  two  tiers  of  16  sections  each  making 
a  total  of  96  sections;  air  warmed  from  — 10°  to  80°;  duct  at 
A  B,  15  sq.  ft.,  velocity  1600  f.  p.  m.;  at  C  D,  9  sq.  ft.,  velocity 
1500  f.  p.  m.;  at  E  F,  1  sq.  ft.,  velocity  1550  f.  p.  m.,  and  at 
G  H,  2.5  sq.  ft.,  velocity  1150  f.  p.  m.;  fresh  air  inlet  grill  48 
sq.  ft.,  covered  by  %"  mesh  wire  screen;  individual  exhaust 
ventilation  for  toilets  and  showers;  automatic  regulation  on 
all  direct  radiation  in  all  class  rooms  and  on  two  of  the  three 
complete  stacks  in  the  vento  heaters.  To  supply  the  coils 
and  the  direct  radiation  required  three  cast  iron  sectional 
boilers,  each  having  a  rated  capacity  of  8350  sq.  ft.  of  direct 
steam  radiation. 


272 


HEATING  AND  VENTILATION 


Fig.  154. 


PLENUM   WARM   AIR   HEATING 


273 


Fig.   155. 


274 


HEATING  AND  VENTILATION 


Fig".   156. 


CHAPTER  XIII. 


DISTRICT     HEATING     OR     CENTRALIZED     HOT     WATER 
AND   STEAM  HEATING. 


GENERAL. 

157.  Heating    Residences    and    Business    Blocks    from    a 
central  station  is  a  method  that  is  being  employed  in  many 
cities  and  towns  throughout  the  country.     The  centralization 
of  the  heat  supply  for  any  district  in  one  large  unit  has  an 
advantage  over  a  number  of  smaller  units  in  being  able  to 
burn  the   fuel  more   economically,   and   in  being  able  to   re- 
duce labor  costs.     It  has  also   the  advantage,  when   in  con- 
nection   with    any    power   plant,    of    saving    the    heat    which 
would  otherwise  go  to  waste  in  the  exhaust  steam  and  stack 
gases,    by   turning    it    into    the   heating   system.      The   many 
electric   lighting  and  pumping  stations   around   the   country 
give   large   opportunity   in   this    regard.      Since    the   average 
steam  power  plant  is  very  wasteful  in  these  two  particulars, 
any  saving  that  might  be  brought  about  should  certainly  be 
sought   for.     On    the   other  -hand,   however,   a  plant   of   this 
kind   is  at  a  disadvantage   in   that  it  necessitates  transmit- 
ting the  heating  medium  through  a  system  of  conduits,  which 
generally  is  a  wasteful  process.     The  failure  of  many  of  the 
pioneer  plants  has  cast  suspicion  upon  all  such  enterprises 
as  paying  investments,  but  the  successful  operation  of  many 
others    shows    the    possibilities,    where    care    is    exercised   in 
their  design  and  operation. 

158.  Important  Considerations  in  Central  Station  Heat- 
ing:— In  any  central  heating  sj'-stem,  the  following  consider- 
rations  will  go  far  toward  the  success  or  the  failure  of  the 
enterprise: 

First. — There  should  be  a  demand  for  the  heat. 

Second. — The  plant  should  be  near  to  the  territory  heated. 

Third. — There  should  be  good  coal  and  water  facilities  at 
the  plant. 

Fourth. — The  quality  of  all  the  materials  and  the  instal- 
lation of  the  same,  especially  in  the  conduit  concerning  in- 


276  HEATING  AND   VENTILATION 

sulation,  expansion  and  contraction,  and  durability,  are 
points  of  unusual  importance. 

Fifth. — The  plant  must  be  operated  upon  an  economical 
basis,  the  same  as  is  true  of  other  plants. 

Sixth. — The  load-factor  of  the  plant  should  be  high.  This 
is  one  of  the  most  important  points  to  be  considered  in  com- 
bined heating-  and  power  work.  The  greater  the  proportion 
of  hours  each  piece  of  apparatus  is  in  operation,  to  the  total 
number  of  hours  that  the  plant  is  run,  the  greater  the  plant 
efficiency.  The  ideal  load-factor  requires  that  all  of  the  ap- 
paratus be  run  at  full  load  all  the  time. 

The  average  conduit  radiates  a  great  deal  of  heat,  hence, 
the  nearer  the  plant  to  the  heated  district  the  greater  the 
economy  of  the  system.  Likewise  a  location  near  a  railroad 
minimizes  fuel  costs,  and  good  water,  with  the  possibility 
of  saving  the  water  of  condensation  from  the  sleam,  assists 
in  increasing  the  economy  of  the  plant.  It  is  to  be  expected 
that  even  a  well  designed  plant,  unless  safeguarded  against 
ills  as  above  suggested,  would  soon  succumb  to  inevitable 
failure. 

Two  types  of  centralized  heating  plants  are  in  use,  hot 
water  and  steam.  Each  will  be  discussed  separately.  In  the 
discussion  of  either  system,  certain  definite  conditions  will 
have  to  be  met.  First  of  all,  there  should  be  a  demand  in 
that  certain  locality  for  such  a  heating  system,  before  the 
plant  can  be  considered  a  safe  investment.  To  create  a  de- 
mand requires  good  representatives  and  a  first-class  resi- 
dence or  business  district.  When  this  demand  is  obtained 
the  plan  of  the  probable  district  to  be  heated  will  first  be 
platted  and  then  the  heating  plant  will  be  located.  In  many 
cases  the  heating  plant  will  be  an  added  feature  to  an  al- 
ready established  lighting  or  power  plant  and  its  location 
will  be  more  or  less  a  predetermined  thing. 

In  addition  to  these  material  and  financial  features  just 
mentioned,  one  must  consider  the  legal  phases  that  always 
come  up  at  such  a  time.  These  relate  chiefly  to  the  franchise 
requirements  that  must  be  met  before  occupying  the  streets 
with  conduit  lines,  etc.  All  of  these  considerations  are  a 
part  of  the  one  general  scheme. 

159.  The  Scope  of  the  Work  in  central  station  heating 
may  be  had  from  the  following  outline: 


DISTRICT   HEATING  21r, 


|  Exhaust  steam  heaters 
Hot  Water  Heating-     Live  steam  heaters 

by  use  of J  Heating-  boilers 

Central  Sta-  1  Economizers 

tion  Heating^  |  Injectors  or 

Com-minglers 

I  Steam  Heating \  Exhaust  steam 

Live  steam 


In  the  hot  water  system  the  return  water  at  a  lowered  tem- 
perature enters  the  power  plant,  is  passed  through  one  or 
more  pieces  of  apparatus  carrying  live  or  exhaust  steam,  or 
flue  gases,  and  is  raised  in  temperature  again  to  that  in  the 
outgoing  main.  From  the  above,  a  number  of  combinations 
of  reheating  can  be  had.  Any  or  all  of  the  units  may  be  put 
in  one  plant  and  the  piping  system  so  installed  that  the 
water  will  pass  through  any  single  unit  and  out  into  the 
main;  or,  the  water  may  be  split  and  passed  through 
units  in  series.  All  of  these  combinations  are  possible,  but 
not  practicable.  In  most  plants,  two  or  three  combinations 
only  are  provided.  In  the  existing  plants  the  order  of  pref- 
erence seems  to  be,  exhaust  steam  reheaters,  economizers, 
heating  boilers,  injectors  or  com-minglers,  and  live  steam 
heaters. 

All  of  the  above  pieces  of  reheating  apparatus  operate 
by  the  transmission  of  heat  through  metal  surfaces,  such  as 
brass,  steel  or  cast  iron  tubes,  excepting  the  com-mingler, 
this  being-  simply  a  barometric  condenser  in  which  the  ex- 
haust steam  is  condensed  by  the  injection  water  from  the  re- 
turn main,  the  mixture  being  drawn  directly  into  the  pumps. 

The  objection  to  the  tube  transmission  is  the  lime,  mud 
and  oil  deposit  on  the  tube  surfaces,  thus  reducing  the  rate 
of  transmission  and  requiring  frequent  cleaning.  The  ob- 
jections to  the  com-minglers  are,  first,  that  the  pump  must 
draw  hot  water  from  the  condenser  and  second,  that  a  cer- 
tain amount  of  the  oil  passes  into  the  heating  line.  With 
perfected  apparatus  for  removing  the  oil,  the  com-mingler 
will  no  doubt  supersede,  to  a  large  degree,  the  tube  re- 
heaters  in  hot  water  heating. 


278  HEATIXd    AND   VENTILATION 

In  the  steam  system  the  proposition  is  very  much  simpli- 
fied. The  exhaust  steam  passes  through  one  or  more  oil 
separating  devices  and  is  then  piped  directly  to  the  header 
leading-  to  the  outgoing  main.  Occasionally  a  connection  is 
made  from  this  line  to  a  condenser,  such  that  the  steam, 
when  not  u3ed  in  the  heating  system,  may  be  run  directly 
to  the  condenser.  These  pipe  lines,  of  course,  are  all  prop- 
erly valved  so  that  the  current  of  steam  may  easily  be  de- 
flected one  way  or  the  other.  In  addition  to  this  exhaust 
steam  supply,  live  steam  is  provided  from  the  boiler  and 
enters  the  header  •  through  a  pressure  reducing  valve.  In 
any  case  when  the  exhaust  steam  is  insufficient  the  supply 
may  be  kept  constant  by  automatic  regulation  on  the  reduc- 
ing valve. 

In  selecting  between  hot  water  and  steam  systems  the 
preference  of  the  engineer  is  very  largely  the  controlling 
factor.  The  preference  of  the  engineer,  however,  should  be 
formed  from  facts  and  conditions  surrounding  the  plant,  and 
should  not  come  from  mere  prejudice.  The  following  points 
are  some  of  the  important  ones  to  be  considered: 

First  cost  of  plant  installed. — This  is  very  much  in  favor  of 
the  steam  system  in  all  features  of  the  power  plant  equip- 
ment, the  relative  costs  of  the  conduit  and  the  outside  work 
being  very  much  the  same  in  the  two  systems. 

Cost  of  operation. — This  is  in  favor  of  the  hot  water  sys- 
tem because  of  the  fact  that  the  steam  from  the  engines 
may  be  condensed  at  or  below  atmospheric  pressure,  while 
the  exhausts  from  the  engines  in  the  steam  systems  must 
be  carried  from  five  to  fifteen  pounds  gage,  which  naturally 
throws  a  heavy  back  pressure  upon  the  engine  piston. 

Pressure  in  circulating  mains. — This  is  in  favor  of  the  steam 
system.  The  pressure  in  any  steam  radiator  will  be  only 
a  few  pounds  above  atmosphere,  while  in  a  hot  water  sys- 
tem, connected  to  high  buildings,  the  pressure  on  the  first 
floor  radiators  near  the  level  of  the  mains  becomes  very 
excessive.  The  elevation  of  the  highest  radiator  in  the 
circuit,  therefore,  is  one  of  the  determining  factors. 

Regulation. — It  is  easier  to  regulate  the  hot  water  system 
without  the  use  of  the  automatic  thermostatic  control,  since 
the  temperature  of  the  water  is  maintained  according  to  a 
local  schedule  which  fits  all  degrees  of  outside  temperature. 


DISTRICT   HEATING  279 

When  automatic  control  is  applied,  this  advantage  is  not  so 
marked. 

Returning  the  water  to  the  power  plant. — In  most  steam  plants 
the  water  of  condensation  is  passed  through  indirect  heaters 
to  remove  as  much  of  the  remaining-  heat  as  possible  and 
is  then  run  to  the  sewer.  This  procedure  incurs  a  consider- 
able loss,  especially  in  cold  weather  when  the  feed  water 
at  the  power  plant  is  heated  from  low  temperatures.  This 
point  is  in  favor  of  the  hot  water  system. 

Estimating  charges  for  heat. — This  is  in  favor  of  the  steam 
system  since,  by  meter  measurement,  a  company  is  able  to 
apportion  the  charges  intelligently.  The  flat  rate  charged 
for  water  heating  and  for  some  steam  heating  is  in  many 
cases  a  decided  loss  to  the  company. 

160.  Conduits: — In  installing  conduits  for  either  hot 
water  or  steam  systems  the  selection  should  be  made  after 
determining,  first,  its  efficiency  as  a  heat  insulator;  second, 
its  initial  cost;  third,  its  durability.  Other  points  that  must 
be  accounted  for  as  being  very  essential  are:  the  supporting, 
anchoring,  grading  and  draining  of  the  mains;  provision  for 
expansion  and  contraction  of  the  mains;  arrangements  for 
taking  off  service  lines  at  points  where  there  is  little  move- 
ment of  the  mains;  and  the  draining  of  the  conduit. 

Some  conduits  may  be  installed  at  very  little  cost  and 
yet  may  be  very  expensive  propositions,  because  of  their  in- 
ability to  protect  from  heat  losses;  while,  on  the  other  hand, 
some  of  the  most  expensive  installations  save  their  first 
cost  in  a  couple  of  years'  service.  Many  different  kinds  of 
insulating  materials  are  used  in  conduit  work  such  as  mag- 
nesia, asbestos,  hair  felt,  wool  felt,  mineral  wool  and  air  cell. 
Each  of  these  materials  has  certain  advantages  and  under 
certain  conditions  would  be  preferred.  It  is  not  the  real 
purpose  here  to  discuss  the  merits  of  the  various  insulators, 
because  the  quality  of  the  workmanship  in  the  conduit  en- 
ters into  the  final  result  so  largely.  The  different  ways  that 
pipes  may  be  supported  and  insulated  in  outside  service  will 
be  given,  with  general  suggestions  only.  Figs.  157  and  158 
show  a  few  of  the  many  methods  in  common  use.  A  very 
simple  conduit  is  shown  at  A.  This  is  built  up  of  wood  sec- 
tions fitted  end  to  end,  covered  with  tarred  paper  to  prevent 
surface  water  leaking  in  and  bound  with  straps.  The  pipe 
either  is  a  loose  fit  to  the  bore  and  rests  upon  the  inner  sur- 


280  HEATING  AND  VENTILATION 

face,  or  is  supported  on  metal  stools,  driven  into  the  wood  or 
merely  resting  upon  it.  Stools  hold  the  pipe  concentric  with 
the  inner  bore  of  the  log.  With  much  end  movement  of  the 
pipe,  from  expansion  and  contraction,  stools  should  not  be 
used  unless  they  are  loose  and  have  a  wide  surface  contact 
with  the  wood.  A  metal  lining  with  the  pipe  resting  di- 
rectly upon  it  is  considered  good.  The  conduit  is  laid  to  a 
good  straight  run  in  a  gravel  bed  and  usually  over  a  small 
tile  drain  to  carry  off  the  surface  water,  excepting  as  this 
drain  is  not  necessary  in  sections  where  there  is  good  gravel 
drainage.  The  insulation  in  A  is  only  fair.  The  air  space 
around  the  pipe,  however,  is  to  be  commended.  B  is  an 
improvement  over  A  and  is  built  up  of  boards  notched  at 
the  edges  to  fit  together.  The  materials  used,  from  the 
outside  to  the  center,  are  noted  on  the  sketch  beginning 
with  the  top  and  reading  down.  This  covering  is  in  general 
use  and  gives  good  satisfaction  from  every  standpoint.  C 
shows  a  good  insulation  and  supports  the  pipe  upon  rollers 
at  the  center  of  a  line  of  halved,  vitrified  tile.  The  lower 
half  of  the  tile  should  be  graded  and  the  pipe  then  run 
upon  the  rollers,  after  which  it  may  be  covered  with  some 
prepared  covering  and  the  remaining  space  next  the  tile 
filled  with  asbestos,  mineral  wool  or  other  like  material.  D 
shows  the  same  adapted  to  basement  work.  Occasionally  two 
pipes  are  run  side  by  side,  main  and  return,  in  which  case 
large  halved  tiles  may  be  used  as  in  E,  having  large  metal 
supports  curved  on  the  lower  face  to  fit  the  tile.  If  these 
supports  are  not  desired  the  same  kind  of  straight  tiles 
may  be  used  with  a  tee  tile  inserted  every  8  to  12  feet 
having  the  bell  looking  down  as  in  F.  In  this  bell  is  built 
a  concrete  setting  with  iron  supports  for  the  pipes  which  run 
on  rollers.  These  rollers  are  sometimes  pieces  of  pipes  cut 
and  reamed,  but  are  better  if  they  are  cast  with  a  curvature 
to  fit  the  pipes  to  be  supported.  This'form  of  conduit,  when 
drained  to  good  gravel,  gives  first-class  service.  G,  H  and  / 
show  box  conduits  with  two  or  more  thicknesses  of  %  inch 
boards  nailed  together  for  the  sides,  top  and  bottom.  The 
bottom  of  the  conduit  is  first  laid  and  the  pipe  is  run.  The 
sides  are  then  set  in  place  and  the  insulating  material  put 
in,  after  which  the  top  is  set  and  the  whole  filled  in.  7  shows 
the  best  form  of  box,  since  with  the  air  spaces  this  is  a 
very  good  insulator.  All  wood  boxes  are  very  temporary, 


DISTRICT    HEATING 


281 


GRAVEL  - 
A5PHALTUM    ' 
WOOD 


-COR  PAPERS 
ASBESTOS      ; 
TIN   LINING       / 
v    MIN    WOOL — ; 
PIPE 
ROLLER 


WOOD 
TILE 

MIN.  WOOL — * 
SECTIONAL      ; 
COVERING^ 
PIPE 
ROLLER 


Fig.  157. 


HEATING  AND   VENTILATION 


STONE- 
BRICK 
;MIN    WOOL 
tWOOD 
SULATION 
PIPE 
ROLLER 
GRAVEL 
DRAIN 


GRAVEL 
WOOD 
-INSULATION 

PIPE 
^— ROLLER 


STONE 

SLATE 
CEMENT/  '-. 
HALVED    TILE 
EC  COVERING 
PIPE 
SUPP 


^STONE 
^CEMENT 

'-PIPE 
SUPPORT 


Fig.  158. 


DISTRICT   HEATING  283 

hence,  brick  and  concrete  are  usually  preferred.  AT  is  a 
conduit  with  8  inch  brick  walls  covered  with  flat  stones  or 
halved  glazed  tiles  cemented  to  place  to  protect  from  sur- 
face leakage.  The  bottom  of  the  conduit  has  supports  built 
in  every  8  to  12  feet,  and  between  these  points  the  conduit 
drains  to  the  gravel.  The  usual  rod  and  roller  here  serve 
as  pipe  supports.  The  pipe  is  covered  with  sectional  cover- 
ing and  the  rest  of  the  space  may  or  may  not  be  filled  with 
wool  or  chips,  as  desired.  L  shows  the  sectional  covering- 
omitted  and  the  entire  conduit  filled  with  mineral  wool,  hair 
felt  or  asbestos.  M  has  the  supporting  rod  built  into  the 
sides  of  the  conduit  and  has  the  bottom  of  the  conduit 
bricked  across  and  cemented  to  carry  the  leaks  and  drainage 
to  some  distant  point.  N  shows  a  concrete  bottom  with 
brick  sides,  having  the  pipe  supported  upon  cast  iron  stand- 
ards. The  latest  conduit  has  concrete  slabs  for  bottom  and 
sides  and  has  a  reinforced  concrete  slab  top.  This  comes  as 
near  being  permanent  as  any,  is  reasonable  in  price,  and 
when  the  interior  is  filled  with  good  non-conducting  ma- 
terial, or  when  the  pipe  is  covered  with  a  good  sectional 
covering,  it  gives  fairly  high  efficiency. 

All  conduit  pipes  should  be  run  as  nearly  uniform  in 
grade  as  possible  to  avoid  the  formation  of  air  and  water 
pockets.  Any  unusual  elevation  in  any  part  of  the  main 
may  require  an  air  vent  being  placed  at  the  uppermost  point 
of  the  curve,  otherwise  air  may  collect  in  such  quantities  as 
to  retard  circulation.  All  low  points  in  the  steam  lines  must 
be  drained  to  traps.  * 

The  heat  Joss  from  conduits  is  an  item  of  considerable  im- 
portance. A  good  quality  of  materials  and  insulation  will 
probably  reduce  this  loss  as  low  as  20  to  25  per  cent,  of  the 
amount  lost  from  the  bare  pipe.  To  show  the  method  of 
analysis  and  to  obtain  an  estimate  of  the  average  conduit 
losses,  the  following  application  will  be  made  to  a  supposed 
two-pipe  hot  water  system.  The  loss  of  heat  in  B.  t.  u.  per 
lineal  foot  from  any  pipe  per  hour  may  be  taken  from  the 
equation 

7f,-   =   KCA   (t  —  t')  (90) 

where  K  =  rate  of  transmission  for  uncovered  pipes,  C  =  100 
per  cent.  —  efficiency  of  the  insulation,  A  =  area  of  pipe  sur- 
face per  lineal  foot  of  pipe,  /  —  average  temperature  on  the 


284 


HEATING  AND  VENTILATION 


inside  of  the  pipe  and  t'  =   average  temperature  on  the  out- 
side of  the  conduit. 

APPLICATION. — Having  given  a  system  of  conduit  pipes 
(two  pipes  in  one  conduit)  with  sizes  and  lengths  as  stated 
in  the  first  and  second  columns  of  Table  XXXVI,  what  is  the 
probable  heat  loss  in  B.  t.  u.  per  hour  on  a  winter  day  and 
what  is  the  radiation  equivalent  in  a  hot  water  system  car- 
rying water  at  an  average  temperature  of  170  degrees? 


TABLE  XXXVI. 


Pipe  size 

Total  lineal 
feet  of  main 

Surface  per 
foot  of  length 

B.  t.  u.  per  hr. 
per  lineal  foot 

Equivalent 
no.  of  sq.  ft. 

inches 

and  return 

A 

He 

of  H.  W.  Rad. 

2 

5000 

.62 

48.8 

1435 

3 

2000 

.91 

71.6 

842 

4 

3000 

1.06 

83.4 

1472 

6 

3000 

1.73 

137.1 

2420 

8 

2000 

•2.-2<> 

177.9 

2093 

10 

2000 

2.83 

221.  !> 

2611 

12 

2000 

3.33 

262.0 

3082 

14 

1000 

4.00 

314.8 

1852 

Totals.    B.  t.  u.  lost  per  hour  2687100 

15807 

If  K  =  2.25,  C  =  100  —  75  =  25  per  cent.,  *  =  175  and 
t'  =  35,  we  have  for  a  2-inch  pipe,  He  =  2.25  X  .25  X  .62  X 
140  =  48.8,  which  for  5000  lineal  feet  =  244000  B.  t.  u.,  and 
for  the  entire  system,  2687100  B.  t.  u.  If  each  square  foot  of 
hot  water  radiation  gives  off  170  B.  t.  u.  per  hour  then  the 
radiation  equivalent  for  the  2-inch  pipe  is  244000  -h  170  = 
1435  square  feet.  Similarly  work  out  for  each  pipe  size  and 
obtain  the  values  given  in  the  last  column  of  the  table.  This 
conduit  loss  is  sufficient  to  heat  15807  square  feet  of  radia- 
tion in  the  district.  In  terms  of  the  coal  pile  it  approxi- 
mates 350  pounds  per  hour.  Now  assuming  the  14  inch  main 
to  supply  the  entire  district  at  a  velocity  of  6  feet  per  second 
we  have  approximately  162000  square  feet  of  H.  W.  surface 
on  the  line.  From  this  the  line  loss  is  15807  -5-  162000  =  9.1 
per  cent.  It  should  be  remembered  that  the  above  assumes 
the  plant  working  under  a  heavy  load,  when  the  per  cent. 


DISTRICT   HEATING  285 

of  line  loss  is  a  minimum.  This  loss  remains  fairly  constant 
while  the  heat  utilized  in  the  district  fluctuates  greatly.  In 
mild  weather,  therefore,  the  per  cent,  of  line  loss  to  the  total 
heat  transmitted  is  much  greater. 

161.  Layout  of  Street  Mains  ami  Conduits: — No  definite 
information  can  be  given  concerning  the  layout  of  street 
mains,  because  the  requirements  of  each  district  would  call 
for  independent  consideration.  The  following  general  sug- 
gestions, however,  can  be  noted  as  applying  to  any  hot 
water  or  steam  system: 

Streets  to  be  used. — Avoid  the  principal  streets  in  the  city, 
especially  those  that  are  paved;  alleys  are  preferred  because 
of  the  minimum  cost  of  installation  and  repairs. 

Cutting  of  the  mains. — Do  not  cut  the  main  trunk  line  for 
branches  more  often  than  is  necessary.  Provide  occasional 
by-pass  lines  between  the  main  branches  at  the  most  im- 
portant points  in  the  system,  so  that,  if  repairs  are  being- 
made  on  any  one  line,  the  circulation  beyond  that  point  may 
be  handled  through  the  by-pass.  Such  by-pass  lines  should 
be  valved  and  used  only  in  case  of  emergency. 

Offsets  and  expansion  joints. — Offsets  in  the  lines  hinder  the 
free  movement  of  the  water  and  add  friction  head  to  the 
pumps;  hence,  in  water  systems,  the  number  should  be  re- 
duced to  a  minimum.  Long  radius  bends  at  the  corners  re- 
duce this  friction.  Offsets  are  especially  valuable  to  take 
up  the  expansion  and  contraction  of  the  piping-  without  the 
aid  of  expansion  joints.  This  is  illustrated  in  Fig.  159,  where 
anchors  are  placed  at  A,  and  the  gradual  bending  of  the 
pipes  at  each  corner  makes  the  necessary  allowance.  The 
expansion  in  wrought  iron  is  about  .00008  inch  per  foot  per 
degree  rise  in  temperature;  hence  in  a  hot  water  main  the 
lineal  expansion  between  0°  and  212°  is  .017  inch  per  foot  of 
length  or  1.7  inches  for  each  100  feet  of  straig-ht  pipe.  In 
hot  water  heating-  systems  the  temperature  of  this  pipe 
would  never  be  less  than  50°,  which  would  cause  an  expan- 
sion from  hot  to  cold  of  only  .013  inch  per  foot,  or  1.3  inches 
for  each  100  feet  of  straight  pipe.  In  steam  systems  the 
pipe  temperature  may  vary  anywhere  from  50°  to  300°, 
making  a  lineal  expansion  of  .02  inch  per  foot  of  length  or  2 
inches  for  each  100  feet  of  straight  pipe.  As  here  shown  the 


286  HEATING  AND  VENTILATION 

movement  from  the  anchor 
at  A  toward  B  may  be  ab- 
sorbed by  the  swinging  of  the 
pipe  about  O.  B.B.  should 
therefore  be  as  long  as  possi- 
ble to  avoid  unduly  straining 
the  pipe  at  the  joints.  Allow- 
Fig.  159.  in&  a  maximum  -movement  of 

6    inches    for    each    expansion 

joint,  the  anchors  would  be  spaced  500  and  300  feet  center 
to  center  respectively,  for  hot  water  and  steam  mains.  These 
figures  would  seldom  be  exceeded,  and  in  some  cases  would 
be  reduced,  the  spacing  depending  upon  the  type  of  expan- 
sion joint  used.  Ordinarily,  400  feet  spacing  can  be  recom- 
mended for  hot  water  and  300  feet  for  steam.  If  the  city 
layout  meets  this  value  fairly  well,  then  the  expansion  joints 
and  anchors  may  be  made  to  alternate  with  each  other,  one 
each  to  every  city  block. 

A  few  of  the  expansion  joints  in  common  use  are  shown 
in  Fig.  160.  A  is  the  old  slip  and  packed  joint.  This  joint 
causes  very  little  trouble  except  that  it  needs  repacking 
frequently.  It  is  very  effective  when  properly  cared  for. 
The  slip  joint  should  have  bronze  bearings  on  both  the 
outside  of  the  plug,  and  the  lining  of  the  sleeve.  The  ends 
of  the  plug  and  sleeve  may  be  screwed  for  small  pipes,  or 
flanged  for  large  ones.  B  shows  an  improved  type  of  slip 
joint,  having  a  roller  bearing  upon  a  plate  in  the  bottom 
of  the  conduit,  and  plugs  bearing  against  metal  plates  along 
the  sides  of  the  conduit  to  keep  it  in  line.  C  and  D  show 
other  slip  joints  very  similar  to  A  and  B.  C  has  one  ball 
and  socket  end  to  adjust  the  joint  to  slight  changes  in  the 
run  of  the  pipe,  and  D  has  two  packings  enclosing  the  plug 
to  give  it  rigidity.  The  drainage  in  each  case  is  taken  off 
at  the  bottom  of  the  casting.  E  has  two  large  flexible  disks 
fastened  to  the  ends  of  the  pipe  and  separated  from  each 
other  by  an  annular  ring  casting.  These  disks  are  frequently 
corrugated,  are  usually  of  copper  and  are  very  large  in 
diameter  so  that  the  pipe  has  considerable  movement  with- 
out endangering  the  metal  in  the  disks.  F  has  a  corrugated 
copper  tube  fastened  at  the  ends  to  the  pipe  flanges.  This 
is  protected  from  excessive  internal  pressure  by  a  straight 
tube  having  a  sliding  fit  to  the  inside  of  the  flanges,  thus 
allowing  for  end  movement.  G  is  very  similar  to  E.  It  has, 


DISTRICT   HEATING 


287 


Fig.  160. 


288 


HEATING  AND  VENTILATION 


however,  only  one  copper  disk.  This  disk  is  enclosed  in  a 
cast  iron  casement,  one  side  of  which  is  open  to  the  at- 
mosphere, the  other  side  having  the  same  pressure  as  within 
the  pipe.  H  is  very  similar  to  E,  having-  two  copper  dia- 
phragms to  take  up  the  movement.  These  diaphragms  flex 
over  rings  with  curved  edges  and  are  thus  protected  some- 
what against  failure.  /  shows  a  copper  U  tube  which  is 
sometimes  used.  This  is  set  in  a  horizontal  position  and  the 
expansion  and  contraction  is  absorbed  by  bending  the  loop. 
In  all  these  joints  those  which  depend  upon  the  bending  of 
the  metal  require  little  attention  except  where  complete 
rupture  occurs.  In  old  plants,  however,  the  rupturing  of 
these  diaphragms  is  of  frequent  occurrence.  The  packed 
joint  requires  attention  for  packing  several  times  in  the 
year,  but  very  seldom  causes  trouble  other  than  this. 

Anchors. — In  any  long  run  of  pipe,  where  the  expansion 
and  contraction  of  the  pipe  causes  it  to  shift  its  position 
very  much,  it  is  necessary  to  anchor  the  pipe  at  intervals  so 
as  to  compel  the  movement  toward  certain  desired  points. 
The  anchor  is  sometimes  combined  with  the  expansion  joint, 
in  which  case  the  conduit  work  is  simplified  (See  Fig.  161). 

Service   pipes   to   residences  are  preferably   taken   off  at 


DISTRICT   HEATING 


289 


or  near  the  anchors.  All  condensation  drains  in  steam  mains 
are  likewise  taken  off  at  such  points. 

Valves. — All  valves  on  "water  systems  should  be  straight- 
way gate  valves.  Valves  on  steam  systems  should  be  gate 
valves  on  lines  carrying  condensation,  and  may  be  renewable 
seat  globe  valves  on  the  steam  lines.  Valves  should  be 
placed  on  the  main  trunk  at  the  power  plant,  on  all  the  prin- 
cipal branch  mains  as  they  leave  the  main  trunk,  on  all 
by-pass  lines,  on  all  the  service  mains  to  the  houses,  and  at 
such  important  points  along  the  mains  as  will  enable  certain 
portions  of  the  heating  district  to  be  shut  off  for  repairs 
without  cutting  out  the  entire  district. 

Manholes. — Manholes  are  placed  at  important  points  along 
the  line  to  enclose  expansion  joints  and  valves.  These  man- 
holes are  built  of  brick  or  concrete  and  covered  with  iron 
plates,  flag  stones,  slate  or  reinforced  concrete  slabs.  Care 
must  be  exercised  to  drain  these  points  well  and  to  have  the 
covering  strong  enough  to  sustain  the  superimposed  loads. 

162.  Typical  Design  for  Consideration: — In  discussing 
district  heating,  each  important  part  of  the  design  work  will 
be  made  as  general  as  possible  and  will  be  closed  by  an 


RE 
1 

StDLNC 

L 

1 
RESIDE 

.NCE 

U 

1 
I 

I 

BUS 

INESS 

1 

| 

1 
X]PL 

ANT 

Fig.  162. 


290 


HEATING  AND   VENTILATION 


application  to  the  following-  concrete  example  which  refers 
to  a  certain  portion  of  an  imaginary  city  (Fig.  162)  as  avail- 
able territory.  A  city  water  supply  and  lighting  plant  is 
located  as  shown,  with  lighting-  and  power  units  aggregat- 
ing- 475  K.  W.,  city  water  supply  pumps  aggregating  3000000 
gallons  maximum  capacity,  and  smaller  pumps  requiring  ap- 
proximately 15  per  cent,  of  the  amount  of  steam  used  by 
the  larger  lighting  units.  It  is  desired  to  re-design  this 
plant  and  to  add  a  district  heating  system  to  it;  the  same  to 
have  all  the  latest  methods  of  operation  and  to  be  of  such  a 
size  as  to  be  economically  handled.  Fig.  169  shows  the  es- 
sential details  of  the  finished  plant. 

Mi.*!.  Electrical  Output  and  Exhaust  Steam  Available  for 
Heating  Purposes  from  the  Power  Units: — In  the  operation 
of  such  a  plant,  one  of  the  principal  assets  is  the  amount  of 
exhaust  steam  available  for  heating  purposes.  The  amount 
may  be  found  for  any  time  of  the  day  or  night  by  construct- 
ing a  power  chart  as  in  Fig.  163,  and  a  steam  consumption 
chart  as  in  Fig.  164.  Referring  to  Fig.  163,  the  values  here 


500 
400 

300^ 
2000 

2.SOKW  UNIT  

-15 

OKW  UN 
5  K>W  UN 
\X  TDTAl 

T  

•M/ 

KW  = 

,PQWLR  UNITS  IN  KW 

^ 

100 

0 

I 

-- 

... 

,_. 

- 

... 

-- 

— 

- 

21    234    56769   10  II    12  1234561    fl   9    10  II    1 

AM                                               M                                                      PM 

HOURS 
Fig.  163. 

given  are  assumed,  for  illustration,  to  be  those  recorded  at 
the  switchboard  of  the  typical  plant  on  a  day  when  heavy 
service  is  required.  The  curves  show  that  the  75  A'.  W.  unit 
runs  from  12  P.  M.  to  7  A.  M.  and  from  6  P.  M.  to  12  P.  M. 
with  an  output  of  25  A'.  W.  It  also  runs  from  7  A.  M.  to  10  A. 
M.  and  from  4  P.  M.  to  6  P.  M.  under  full  load.  The  150  A'.  11'. 


DISTRICT   HEATING 


291 


unit  runs  from  4  A.  M.  to  7  A.  M.  with  an  output  of  100  A'.  W. 
and  then  increases  to  125  A'.  W.  for  the  entire  time  until  6  P.  M. 
when  it  is  shut  down.  The  250  K.  W.  unit  is  started  up  at  7 
A.  M.  and  runs  until  6  P.  M.  under  full  load,  when  the  load 
drops  off  to  150  K.  W.  and  continues  until  10  P.  M.  when  the 
unit  is  shut  down,  leaving  only  the  75  K.  W.  unit  running. 
The  heavy  solid  line  shows  all  the  power  curves  superim- 
posed one  upon  the  other.  Having  given  the  A'.  W.  output, 
the  general  equation  for  determining  the  horse-power  of  the 
engines  is 

K.  W.   X    1000 
/.  II.  P.   =   (9D 

746   X  E  X  E' 

where  E  and  E'  are  the  efficiencies  of  the  generator  and  en- 
gine respectively.  If  we  assume  the  efficiency  of  the  gener- 
ator to  be  90  per  cent.,  and  that  of  the  engine  to  be  92  per 
cent.,  then  Equation  91  becomes 

K.  W.   X    1000 

I   H   P    =  -  =  approx.  1.62  A'.  W.        (92) 

746  X  .90  X  .92 

Assuming  that  the  250  K.  W.  unit  consumes  24  pounds,  the 
150  K.  W.  unit  32  pounds,  and  the  75  A.  W.  unit  32  pounds  of 
steam  per  /.  H.  P.  hour  respectively,  when  running  under 


I 

22 

HI 

?i1l 

Q 

?(] 

Dttf 

2Q 

as 

i«fi 

in 

l"ifl 

nn 

§ 

TAM  OON5 

IM 

JJ 

(  IIS 

1 

OF 

53 

M' 

}     | 

Mr 

"S 

yaj 

^F 

49 

n—1 

5fe 

12    I    234    56789    10  1 1    12   I    234    567    89IQH    12 
AM  M  PM 

HOURS 
Fig.  164. 


292  HEATING  AND  VENTILATION 

normal  loads,  the  total  steam  consumed  in  the  three  units 
at  any  time  is  shown  by  the  lower  curve  in  Fig.  164.  The 
upper  curve  shows  the  15  per  cent,  added  allowance  for 
smaller  units  not  included  in  the  above  list.  The  values 
assumed  for  efficiencies  and  the  values  for  steam  consump- 
tion are  reasonable  and  may  be  used  if  a  more  exact  figure 
is  not  to  be  had. 

It  will  be  seen  that  the  maximum  steam  consumption  in 
the  generating  units  in  the  power  plant  is  23100  pounds  per 
hour  and  the  minimum  is  1490  pounds  per  hour.  These  two 
amounts,  together  with  the  exhaust  steam  from  the  circu- 
lating pumps  on  the  heating  system,  if  a  hot  water  system 
is  installed,  and  that  from  the  pumps  in  the  city  water 
supply,  will  determine  the  capacity  of  the  exhaust  steam 
heaters  on  the  hot  water  supply  and  the  capacity  of  the 
boilers  or  economizers  to  be  used  as  heaters  when  the 
exhaust  steam  is  deficient. 

164.  Amount  of  Heat  Available  for  Heating  Purposes 
in  Exhaust  Steam,  Compared  with  That  in  Saturated  Steam 
at  the  Pressure  of  the  Exhaust: — To  study  the  effect  of  ex- 
haust steam  upon  heating  problems  and  to  determine,  if 
possible,  the  theoretical  amount  of  heat  given  off  with  the 
exhaust  steam  under  various  conditions  of  use,  make  several 
applications:  first,  to  a  simple  high  speed  non-condensing 
engine  using  saturated  steam;  second,  to  a  compound  Corliss 
non-condensing  engine  using  saturated  steam;  third,  to  the 
first  application  when  superheated  steam  is  used  instead  of 
saturated  steam;  and  fourth,  to  a  horizontal  reciprocating 
steam  pump.  Assume  the  following  safe  conditions.  Case 
one — boiler  pressure  100  pounds  gage;  pressure  of  steam 
entering  cylinder  97  pounds  gage;  quality  of  steam  at 
cylinder  98  per  cent.;  steam  consumption  34  pounds  per 
indicated  horse-power  hour;  one  per  cent,  loss  in  radiation 
from  cylinder;  and  exhaust  pressure  2  pounds  gage.  Case 
two — boiler  pressure  125  pounds  gage;  pressure  at  high 
pressure  cylinder  122  pounds  gage;  quality  of  steam  enter- 
ing high  pressure  cylinder  98  per  cent.;  steam  consumption 
22  pounds  per  indicated  horse-power  hour;  2  per  cent,  loss 
in  radiation  from  cylinders  and  receiver  pipe,  and  exhaust 
pressure  2  pounds  gage.  Case  three — same  as  case  one  with 
superheated  steam  at  150  degrees  of  superheat.  Case  four — 
as  stated  later. 


DISTRICT   HEATING  293 

The  number  of  B.  t.  u.  exhausted  with  the  steam,  in 
any  case,  is  the  total  heat  in  the  steam  at  admission,  minus 
the  heat  radiated  from  the  cylinder,  minus  the  heat  ab- 
sorbed in  actual  work  in  the  cylinder. 

High  speed  engine.  Case  one. — Let  r  —  heat  of  vaporiza- 
tion per  pound  of  steam  at  the  stated  pressure,  x  =.  quality 
of  the  steam  at  cut-off,  q  —  heat  of  the  liquid  in  the  steam 
per  pound  of  steam,  and  Ws  =•  pounds  of  steam  per  indicated 
horse-power  hour.  From  this  the  total  number  of  B.  t.  u. 
entering-  the  cylinder  per  horse-power  hour  is 

Total  B.  t.  u.  =  Ws   (xr  +  q)  (93) 

From  Table  4,  r  =  881,  x  =  .98  and  q  =  307;  then  if  W»  =  34, 
initial  B.  t.  u.  =  34  (.98  X  881  +  307)  =  39792.92.  Deducting- 
the  heat  radiated  from  the  cylinder  we  have  39792.92  X  .99  = 
39395  B.  t.  u.  per  horse-power  left  to  do  work.  The  B.  t.  u. 
absorbed  in  mechanical  work  (useful  work  +  friction)  in 
the  cylinder  per  horse-power  hour  is  (33000  X  60)  -T-  778  = 
2545  B.  t.  u.  Subtracting-  this  work  loss  we  have  39395  - 
2545  =  36850  B.  t.  u.  given  up  to  the  exhaust  per  horse-power 
hour.  Comparing-  this  value  with  the  total  heat  in  the  same 
weight  of  saturated  steam  at  2  pounds  gage,  we  have 
100  X  36850  -r-  (34  X  1152.8)  =  94  per  cent. 

Compound  Corliss  engine.  Case  two. — With  the  same  terms 
as  above  let  r  =  869,  x  =  .98,  q  =  322.8,  and  Ws  =  22,  then 
the  initial  B.  t.  u.  =  22  (.98  X  869  +  322.8)  =  25837.  Less 
2  per  cent,  radiation  loss  =  25837  X  -98  =  25321  B.  t.  u. 
The  loss  absorbed  in  doing  mechanical  work  in  the  cylinder 
per  horse-power  is,  as  before,  2545  B.  t.  u.  Subtracting  this 
we  have  25321  —  2545  =  22776  B.  t.  u.  given  up  to  the  ex- 
haust per  horse-power  hour.  Comparing-  as  before  with 
saturated  steam  at  2  pounds  gage,  we  have  100  X  22776  -r- 
(22  X  1152.8)  =  90  per  cent. 

Case  three. — Now  suppose  superheated  steam  be  used  in 
the  first  application,  all  other  conditions  being  the  same, 
the  steam  having  150  degrees  of  superheat,  what  difference 
will  this  make  in  the  result?  The  total  heat  entering1  the 
cylinder  now  is  the  total  heat  of  the  saturated  steam  at 
the  initial  pressure  plus  the  heat  g-iven  to  it  in  the  super- 
heater. Let  cp  —  specific  heat  of  superheated  steam  and 


294  HEATING  AND  VENTILATION 

id    =    the   degrees   of  superheat,   then    the   total  heat   of  the 
superheated  steam  is 

Total  B.  t.  u.   (sup.)   =  W*   (xr  +  q  -f  r,,t,i)  (94) 

This  for  one  horse-power  of  steam  (34  pounds),  if  the 
specific  heat  of  superheated  steam  is  .54,  will'be  34  X  .99  X 
(1188  +  .54  X  150)  =  42714.5  B.  t.  u.  and  the  heat  turned 
into  the  exhaust  will  be  42714.5  —  2545  =  40169.5  B.  t.  u. 
Comparing-  this  with  the  heat  in  saturated  steam  at  2  pounds 
gage,  we  have  100  X  40169.5  -=-  (34  X  1152.8)  =  102  per  cent. 

Case  four. — Pump  exhausts  are  sometimes  led  into  the 
supply  and  used  for  heating  purposes  along  with  the  engine 
exhausts.  If  such  conditions  be  found,  what  is  the  heating 
value  of  such  steam?  Assume  the  live  steam  to  enter  the 
steam  cylinder  of  the  pump  under  the  same  pressure  and 
quality  as  recorded  for  the  high  speed  engine.  The  steam 
is  cut  off  at  about  %  of  the  stroke  and  expands  to  the  end 
of  the  stroke.  With  this  small  expansion  the  absolute 
pressure  at  the  end  of  the  stroke  will  be  approximately 
%  X  112  =  98  pounds,  and  if  enough  heat  is  absorbed  from 
the  cylinder  wall  to  bring  the  steam  up  to  saturation  at 
the  release  pressure,  we  will  have  a  total  heat  above  32 
degrees,  in  the  exhaust  steam  per  pound  of  steam  at  98 
pounds  absolute,  of  1186  B.  t.  u.  Comparing  this  with  a 
pound  of  saturated  steam  at  2  pounds  gage,  we  have 
100  X  1186  ~  1152.8  =  103  per  cent.  Under  the  conditions 
such  as  here  stated  with  a  high  release  pressure,  a  small 
expansion  of  steam  in  the  cylinder  and  dry  steam  at  the 
end  of  the  stroke,  it  is  possible  to  suddenly  drop  the  pressure 
from  pump  release  to  a  low  pressure,  say  2  pounds  gage, 
and  have  all  the  steam  brought  to  a  state  approaching 
superheat.  It  is  not  likely,  however,  that  the  steam  is  dry 
at  the  end  of  the  stroke  in  any  pump  exhaust,  because  the 
heat  lost  in  radiation  and  in  doing  work  in  the  slow  moving 
pump  would  be  such  as  to  have  a  considerable  amount  of 
entrained  water  with  the  steam,  thus  lowering  the  quality 
of  the  steam.  These  above  conditions  are  extreme  and  are 
not  obtained  in  practice. 

From  cases  one  and  two  it  would  appear  that  the 
f/reatest  amount  of  heat  that  can  be  expected  from  engine 
exhausts,  for  use  in  heating  systems  at  or  near  the  pres- 
sure of  the  atmosphere,  is  90  to  94  per  cent,  of  that  of 


DISTRICT   HEATING  295 

saturated  steam  at  the  same  pressure.  The  percentage  will, 
in  most  cases,  drop  much  below  this  value.  All  things  con- 
sidered, exhaust  steam  having  80  to  85  per  cent,  of  the  value  of 
saturated  steam  at  the  same  pressure  is  probably  the  safest  ratine? 
when  calculating  the  amount  of  radiation  which  can  be  supplied  by 
the  engines.  In  many  cases  no  doubt  this  could  be  exceeded, 
but  it  is  always  best  to  take  a  safe  value.  On  the  other  hand, 
when  figuring  the  amount  of  condenser  tube  surface  or  reheater  tube 
surface  to  condense  the  steam,  it  would  be  best  to  take  exhaust  steam 
at  100  per  cent,  quality,  since  this  would  be  working  toward 
the  side  of  safety. 

In  plants  where  the  exhaust  steam  is  used  for  heating 
purposes  and  where  the  amount  supplied  by  direct  acting 
steam  pumps  is  large  compared  with  that  supplied  by  the 
power  units,  it  is  possible  to  have  the  quality  of  the  ex- 
hausts anywhere  between  800  and  1000  B.  t.  u.  per  pound 
of  exhaust.  It  should  be  understood  that  saturated  steam 
at  any  stated  pressure  always  has  the  same  number  of 
B.  t.  u.  in  it,  no  matter  whether  it  is  taken  directly  from 
the  boiler,  or  from  the  engine  exhaust.  A  pound  of  the 
mteture  of  steam  and  entrained  water,  taken  from  engine 
exhausts,  should  not  be  considered  as  a  pound  of  steam. 
If  we  are  speaking  of  a  pound  of  exhaust  steam  without 
the  entrained  water  as  compared  with  a  pound  of  saturated 
steam  at  the  same  pressure,  they  are  the  same,  but  a  pound 
of  engine  exhaust  or  mixture  is  a  different  thing. 

HOT  WATER  SYSTEMS. 

105.  Four  General  Classifications  of  hot  water  heating 
may  be  found  in  current  work,  two  applying  to  the  conduit 
piping  system  and  two  to  the  power  plant  piping  system. 
The  first,  known  as  the  one-pipe  complete  circuit  system,  is  shown 
in  Fig.  165.  It  will  be  noticed  that  the  water  leaves  the 
power  plant  and  makes  a  complete  circuit  of  the  district, 
as  A,  B,  C,  D,  E,  F,  G,  through  a  single  pipe  of  uniform 
diameter.  From  this  main  are  taken  branch  mains  and 
leads  to  the  various  houses,  as  a,  6,  c  and  d,  e,  each  one 
returning  to  the  'principal  main  after  having  made  its  own 
minor  circuit.  The  second  is  known  as  the  tioo-pipe  high 
pressure  system,  in  which  two  main  pipes  of  like  diameter 
laid  side  by  side  in  the  same  conduit,  radiate  from  the  power 
plant  to  the  farthest  point  on  the  line  reducing  in  size  at 
certain  points  to  suit  the  capacity  of  that  part  of  the  district 


296 


HEATING  AND  VENTILATION 


served.  This  system  is  represented  by  Fig.  166.  In  the 
one-pipe  system  the  circulation  in  the  various  residences  is 
maintained,  in  part,  by  what  is  known  as  the  shunt  system, 
and  in  part,  by  the  natural  gravity  circulation.  The  circu- 
lation in  the  two-pipe  system  is  maintained  by  a  high 
differential  pressure  between  the  main  and  the  return  at 
the  same  point  of  the  conduit.  The  force  producing  move- 
ment of  the  water  in  the  shunt  system  is,  therefore,  very 
much  less  than  in  the  two-pipe  system.  As  a  consequence, 


POWER  HOUSE 
Fig.  165. 

the  one-pipe  system  has  a  lower  velocity  of  the  water  in  the 
houses  and  larger  service  pipes  than  the  two-pipe  system. 

In  many  cases  it  is  desired  to  connect  central  heating 
mains  to  the  low  pressure  hot  water  systems  in  private 
plants.  Such  connections  may  easily  be  made  with  either 
one  of  the  two  systems  by  installing  some  minor  pieces 
of  apparatus  for  controlling  the  supply. 

The  third  and  fourth  classifications,  the  open  and  closed 
systems,  have  about  the  same  meaning  as  when  applied  to 
gravity  work  in  isolated  plants.  The  first  is  open  to  the 
atmosphere  at  some  point  along  the  circulating  system, 
usually  at  the  expansion  tank  which  is  placed  on  the  return 
line  just  before  the  circulating  pumps.  The  closed  system 
presupposes  some  form  of  regulation  for  controlling  exces- 
sive or  deficient  pressures  without  the  aid  of  an  expansion 
tank.  In  such  cases  pumps  with  automatic  control  may  be 
used  for  taking  care  of  the  reserve  supply  of  water.  In  the 


DISTRICT   HEATING 


297 


open  system  the  exhaust  steam  may  be  injected  directly  into 
the  return  circulating  water  by  the  use  of  an  open  heater 
or  a  com-ming-ler.  The  open  heater  and  com-mingler  cannot 
be  used  on  the  pressure  side  of  the  pumps.  Surface  con- 
densers or  reheaters,  heating-  boilers  and  economizers  may 
be  used  on  either  open  or  closed  systems. 


POWER  Hou&t 
Fig.  166. 

166.  Amount  of  Water  Needed  per  Hour  as  a  Heating 
Medium: — All  calculations  must  necessarily  begin  with  the 
heat  lost  at  the  residence.  Referring  to  the  •  living  room, 
Table  XX,  the  heat  loss  is  15267  B.  t.  u.  per  hour,  requiring 
91  square  feet  of  hot  water  heating  surface  to  heat  the 
room.  Let  the  circulating  water  have  the  following  temper- 
atures: leaving  the  power  plant  180°,  entering  the  radiator 
177°,  leaving  the  radiator  157°,  and  entering  the  power 
plant  155°.  According  to  these  figures,  which  may  be  con- 
sidered fair  average  values,  the  water  gives  off  to  the 
radiator  20  B.  t.  u.  per  pound  or  166.6  B.  t.  u.  per  gallon,  thus 
requiring  15267  -f-  166.6  =  91  gallons  of  water  per  hour  to 
maintain  the  room  at  a  temperature  of  70°.  From'  this  a 
safe  estimate  may  be  given  for  design,  allow  one  gallon  of 
water  per  hour  for  each  square  foot  of  hot  water  heating  surface  in 
the  district.  In  a  plant  operating  under  high  efficiency  this 
may  be  reduced  to  6  pounds  per  square  foot  per  hour.  It  is 
very  certain  that  some  plants  are  designed  to  supply  less 
than  one  gallon,  but  in  such  cases  it  requires  a  higher  tern- 


298  HEATING  AND  VENTILATION 

perature  of  the  circulating  water  and  allows  little  chance 
for  future  expansion  of  the  plant.  A  drop  of  20  degrees, 
i.  e.,  20  B.  t.  u.  heat  loss  per  pound  of  water  passing  through 
the  radiator,  is  probably  the  most  satisfactory  basis.  All 
things  considered,  the  above  italicised  statement  will  satisfy 
every  condition.  (See  Art.  173).  Having  the  total  number 
of  square  feet  of  radiation  in  the  district,  the  total  amount 
of  water  circulated  through  the  mains  per  hour  can  be 
obtained,  after  which  the  size  of  the  pumps  in  the  power 
plant  may  be  estimated. 

167.  Radiation   in   the   District: — The   amount   of   radia- 
tion that  may  be  installed  in  the  district  is  problematical.    In 
an  average  residence  or  business  district  the  following  fig- 
ures may  easily  be   realized:    business   block,  9000  square  feet; 
residence  block,  4^00  square  feet.     In  certain  locations  these  fig- 
ures may  be   exceeded   and   in  others  they  may   be   reduced. 
Where  the  needs  of  the  district  are  thoroughly  understood  a 
more  careful  estimate  can  easily  be  made.     It  is  always  well 
to  make  the  first  estimate  a  safe  one  and  any  possible   in- 
crease above   this   figure   could  be   taken   care   of  as   in   Art. 
166.      Referring   to   Fig.    162,   an   estimate   of   the   amount   of 
radiation   that   may   be   expected    in   this   typical   case,    if   we 
assume  ten  business  blocks  and  twenty-one  residence  blocks, 
is  184500  square  feet.     This  will  call  for  the   circulation   of 
184500  gallons  of  water  per  hour. 

168.  Future  Increase  in  Radiation: — From  the  tempera- 
tures given  in  Art.   166,  it  will  be  seen  that  each  pound  of 
water  takes  on  25  B.  t.  u.  at  the  power  plant  and  that  there 
is  a  possible  increase  of  212  —  180   =   32  B.  t.  u.  per  pound 
that  may  be  given  to  it,  thus  increasing  the  capacity  of  the 
system  approximately  125  per  cent.     It  would  not  be  safe  to 
count  on  such  an  increase  in  the  average  plant  because  of  a 
defective  layout  in   the   piping  system   or  because   of  a  low 
efficiency   in  some  of  the  pumps  or   other   apparatus  in   the 
plant.      If,    however,    a   plant    is    installed    according    to    the 
above  figures,  the  capacity  may  be  quite  materially  increased 
by  increasing  the  temperature  of  the  outgoing  water  at  the 
plant  to  212°. 

169.  The  Pressure  of  the  Water  in  the  Mains: — The  ele- 
vation above  the  plant  at  which  a  central  station  can  supply 
radiation  is  limited.     Water  at  180°  will  weigh  60.55  pounds 


DISTRICT   HEATING  299 

per  cubic  foot,  and  the  pressure  caused  by  an  elevation  of  1 
foot  is  .42  pound  per  square  inch.  From  this  the  static  pres- 
sure at  the  power  plant,  due  to  a  hydraulic  head  of  100  feet, 
is  42  pounds  per  square  inch.  This  value  should  not  be  ex- 
ceeded, and  generally,  because  of  the  influence  it  has  on  the 
machines  and  pipes  toward  producing  leaks  or  complete 
ruptures,  a  less  head  than  this  is  desirable.  A  static  pres- 
sure of  42  pounds  may  be  expected  to  produce,  in  a  well  de- 
signed plant,  an  outflow  pressure  of  65  to  75  pounds  per 
square  inch  and  a  return  pressure  of  15  to  20  pounds  per 
square  inch,  when  working  under  fairly  heavy  service.  In 
any  case  where  the  mains  are  too  small  to  supply  the  radia- 
tion in  the  system  properly,  we  may  expect  the  value  given 
for  the  outflow  to  increase  and  that  for  the  return  to  de- 
crease. A  safe  set  of  conditions  to  follow  is:  head,  in  feet, 
60;  static  pressure,  in  pounds  per  square  inch,  25;  outgoing 
pressure  at  the  pumps,  in  pounds  per  square  inch,  50;  return 
pressure  at  the  pumps,  in  pounds  per  square  inch,  5.  This 
differential  pressure  of  45  pounds  is  caused  by  the  friction 
losses  in  the  piping  system,  pumps  and  heaters.  .Long  pipe 
systems,  as  these  are  called,  have  much  greater  friction  losses 
in  the  long  runs  of  piping  than  in  the  ells,  tees,  valves,  etc., 
hence,  the  friction  head  of  the  pipes  is  all  that  is  usually 
considered.  Where  the  minor  losses  are  thought  to  be  large, 
they  may  be  accounted  for  by  adding  to  the  pipe  loss  a 
certain  percentage  of  itself,  say  10  to  20  per  cent.  Pump 
power  is  figured  from  the  differential  pressure. 

The  maximum  and  minimum  pressures  in  the  system  are 
due  to  two  causes:  first,  the  static  head,  and  second,  the 
frictional  resistances.  These  extremes  of  pressure  are  ap- 
proximately— static  head  plus  (or  minus)  one-half  the  frictional 
resistances.  To  obtain  the  frictional  resistances,  Chezy's 
Equation  95,  is  recommended.  See  Merriman's  "A  Treatise 
on  Hydraulics,"  Arts.  86  and  100,  and  Church's  "Mechanics 
of  Engineering,"  Art.  519. 

40Z  v- 

hf  =  -    -  X   —  (95) 

d  2g 

where  lit  =  feet  of  head  lost  in  friction,  0  =  friction  factor 
(synonymous  with  coefficient  of  friction.  For  clean  cast 
iron  pipes  with  a  velocity  of  5  to  6  feet  per  second  this 
has  been  found  to  vary  from  .0065  to  .0048  for  diameters 
between  3  and  15  inches  respectively.  .005  is  suggested  as 


300  HEATING  AND  VENTILATION 

a  safe  average  value  to  use),  I  =  length  of  pipe  in  feet, 
v  =  velocity  of  water  in  feet  per  second,  d  =  diameter 
of  pipe  in  feet  and  2g  —  64.4. 

APPLICATION.  —  In  Fig.  166,  let  it  be  desired  to  find  the 
differential  pressure  at  the  pumps  due  to  the  friction  losses 
in  the  line  A,  B,  C,  D,  E.  The  lengths  of  the  various  parts 
are:  power  plant  to  A,  200  feet;  A  to  B,  500  feet;  B  to  C, 
1500  feet;  C  to  D,  1500  feet;  and  D  to  E,  500  feet.  Assume, 
for  illustration,  that  the  total  radiation  in  square  feet 
beyond  each  of  these  points  is:  power  plant,  125000;  A,  85000; 
B,  50000;  C,  28000;  and  D,  12000.  This  requires  125000,  85000, 
50000,  28000  and  12000  gallons  of  water  per  hour,  or  4.74, 
3.27,  1.75,  1  and  .44  cubic  feet  of  water  per  second,  respec- 
tively, passing  these  points.  Now,  if  the  velocities  be 
roughly  taken  at  6  and  5  feet  per  second,  (pipes  near  the 
power  plant  may  be  given  somewhat  higher  velocities  than 
those  at  some  distance  from  the  plant),  the  pipes  will  be  12, 
10,  8,  6  and  4  inches  diameter.  In  applying  the  equation  to 
one  part  of  the  line  we  show  the  method  employed  for  each. 
Take  that  part  from  the  power  plant  to  A.  •  With  v  =  6 

4   X    .005    X    200    X   36 

=  2.2  feet. 


64.4    X    1 

It  should  be  noted  here  that  Equation  95  refers  to  pipes 
where  all  the  water  that  enters  at  one  end  passes  out  the  other. 
This  is  not  true  in  heating  mains  where  a  part  of  the  water 
is  drawn  off  at  intermediate  points.  On  the  other  hand, 
Merriman  (Art.  99)  explains  that  a  water  service  main,  where 
the  water  is  all  taken  off  from  intermedite  tappings  and  where 
the  velocity  at  the  far  end  is  zero,  causes  only  one-third  of  the 
friction  given  by  the  above  equation.  The  case  under  con- 
sideration falls  somewhere  between  these  two  extremes,  the 
part  next  the  power  plant  approaching  the  former  and  the 
last  part  of  the  line  exactly  meeting  the  conditions  of  the 
latter.  Assuming  the  mean  of  these  two  conditions,  which 
is  probably  very  close  to  the  actual,  gives  two-thirds  of  that 
found  by  the  equation.  Now  since  this  is  a  double  main 
system,  i.  e.,  main  and  return  of  the  same  size,  the  friction 
head  for  the  two  lines  becomes  2.94  feet,  from  the  power 
plant  to  A.  In  a  similar  way  the  other  parts  may  be  tried 
and  the  results  from  the  entire  line  assembled  in  convenient 
form  as  in  Table  XXXVII. 


DISTRICT   HEATING 
TABLE  XXXVII. 


301 


P.P. 
to  A. 

AtoB 

BtoC 

CtoD 

DtoE 

Distance  between  points  
Radiation  supplied  
Volume  of  water  passing 

200 
125000 

500 
85000 

1500 
50000 

1500 
28000 

500 
12000 

point  in  cu.  ft.  per  sec  

4.74 

3.27 

1.75 

1. 

.44 

Velocity  f    p.   s  

g 

c 

Area  of  pipe  sq    ft  

79 

545 

or; 

20 

087 

Diana   of  pipe  in  ft  

1 

83 

66 

5 

33 

Jif  by   (73)   for  flow  main  

2  ? 

6  7 

17  4 

23  3 

11  7 

hf    (taking  %  value) 

1  47 

4  47 

11  6 

15  5 

7  8 

hf  (%  val.  flow  and  return)  

2.94 

8.94 

23.2 

31.0 

15.6 

From  the  last  line  of  the  table  obtain  the  total  friction 
head  for  both  mains,  not  including  ells,  tees,  valves,  etc., 
to  be  81.6  feet.  This  is  equivalent  to  34.3  pounds  per  square 
inch.  Allowing-  20  per  cent,  of  all  the  line  losses  to  cover 
the  minor  losses  we  have  approximately  40  pounds  differen- 
tial pressure,  which  is  a  reasonable  value. 

Another  approximate  method  of  analyzing  this  problem  is  to 
assume  the  amount  of  water  passing  any  run  of  main  to  be 
the  total  requirement  beyond  the  run  plus  one-half  of  that 
amount  taken  off  through  the  tappings  along  the  run  and 
estimate  the  friction  head  from  this  figure.  This  plan  will 
call  for  the  full  value  of  Equation  95  and  not  the  two-thirds 
value  as  before.  As  an  illustration,  allowing  one  gallon  of 
water  per  square  foot  of  radiation  per  hour,  approximately 
125000  gallons  pass  from  P.  P.  to  A.  Some  of  this  is  taken 
off  in  tappings  and  the  rest  of  40000  is  taken  off  through  the 
branch  main.  85000  pass  A  and  35000  are  taken  off  through 
the  tappings  to  11.  50000  pass  B  and  22000  are  taken  off 
through  tappings  to  C.  28000  pass  C  and  16000  are  taken  off 
to  D.  12000  pass  D  and  all  are  taken  through  tappings  to  E, 
the  end  of  the  line. 

The  amount  of  water  chargeable  to  each  run  will  be: 
P.  P.  to  A,  125000,  A  to  B,  50000  +  35000  4-  2  —  67500,  B  to  (7, 
28000  +  22000  -f-  2  =  39000,  C  to  D,  12000  +  16000  -f-  2  — 
20000,  and  from  D  to  E,  12000  -=-  2  =  6000  gallons  per  hour. 
Reduced  to  cu.  ft.  per  sec.  this  is  P.  P.  to  A,  4.7,  A  to  B,  2.5, 
B  to  C,  1.44,  C  to  D,  .74,  and  D  to  E,  .44. 


302 


HEATING  AND  VENTILATION 


For  purpose  of  comparing  with  preceding-  method,  vol- 
umes, velocities,  pipe  sizes  (the  same  as  in  Table  XXXVII) 
and  friction  heads  are  shown  in  Table  XXXVIII. 


TABLE   XXXVIII. 


PPto 
A 

A  toB 

BtoC 

CtoD 

D  toE 

Volume  passing  through  section, 
cu.  ft.  per  sec. 

4.7 

2.5 

1.44 

.74 

.44 

Average  velocity  in  f.  p.  s.     

6 

4.6 

4.1 

5. 

Area  of  pipe  in  sq.  ft. 

.79 

.545 

.35 

.20 

.087 

Diam.  of  pipe  in  ft.                

.83 

.66 

.5 

.33 

hf  by  (95)   flow  and  return  

4.4 

2.34 

23.6 

25.6 

23.4 

Total  friction  head  =  79.  34  ft.  not  including  ells,  tees,  valves,  etc. 

170.  Velocity  of  the  Water  in  the  Mains  and  the  Dia- 
meter of  the  Mains: — The  district  is  first  chosen  and  the 
layout  of  the  conduit  system  is  made.  This  is  done  inde- 
pendently of  the  sizes  of  the  pipes.  When  this  layout  is 
finally  completed,  the  pipe  sizes  are  roughly  calculated  for 
all  the  important  points  in  the  system  and  are  tabulated 
in  connection  with  the  friction  losses  for  these  parts,  as 
in  Art.  169.  When  this  is  done,  Equation  96,  which  is  rec- 
ommended to  be  used  in  connection  with  Equation  95,  may  be 
applied  and  the  theoretical  diameters  found.  (The  approxi- 
mate diameters  and  the  friction  heads  need  not  be  calcu- 
lated in  Equation  95  for  use  in  Equation  96,  'providing  some 
estimate  may  be  made  for  the  value  of  Jif,  for  the  various 
lengths  of  pipe.  If  desired,  hf  may  be  assumed  without  any 
reference  to  the  diameter,  but  this  is  a  rather  tedious  proc- 
ess. For  discussion  of  this  point  see  Church's  Hydraulic 
Motors,  Arts.  121-124  b.) 


=  .629       % 


X 


(96) 


where  d,  lit,  0  and  I  are  the  same  as  in  Equation  95,  and  Q  = 
cubic  feet  of  water  passing  through  the  pipe  per  second. 
This  equation  differs  from  those  given  in  the  references 
stated,  in  that  the  term  %  is  inserted  as  a  mean  value  be- 
tween the  two  extreme  conditions,  as  stated  in  Art.  169. 


DISTRICT   HEATING  303 

APPLICATION.  —  Let  it  be  desired  to  find  the  diameter  for 
the  single  main  between  the  power  ,plant  and  A,  Art.  169, 
with  hf  =  1.47 

r     2  X  .005  X  200  X   (4.74)2 


d  =  .629 


~|  % 

-  1  ft.  =  12  in. 


3  X  1.47 

Applying-  to  the  entire  line  with  hf  as  given  in  next  to  last 
line  of  Table  XXXVII,  gives  power  plant  to  A,  d  =  12  inches; 
.1  to  B,  d  =  10  inches;  B  to  C,  d  =  8  inches;  C  to  D,  d  =  6 
inches;  and  D  to  E,  d  =  4  inches. 

In  some  cases,  when  close  estimating  is  not  required, 
it  is  satisfactory  to  assume  a  velocity  of  the  water  and  find 
the  diameter  without  considering  the  friction  loss.  In  many 
cases,  however,  this  would  soon  prove  a  positive  loss  to  the 
company.  With  a  low  velocity,  the  first  cost  would  be  large 
and  the  operating  cost  would  be  low.  On  the  other  hand, 
if  the  velocity  were  high,  the  first  cost  would  be  small  and 
the  operating  cost  and  depreciation  would  be  large.  As  an 
illustration  of  how  the  friction  head  increases  in  a  pipe  of 
this  kind  with  increased  velocity,  refer  to  the  run  of  mains 
between  B  and  C.  Assuming  a  velocity  of  10  feet  per 
second,  which  in  this  case  would  be  very  high,  the  friction 
head,  Jif,  for  the  single  main,  becomes  62  and  the  theoretical 
diameter  is  5.5,  say  6  inches.  The  friction  head,  as  will  be 
seen,  is  5.4  times  the  corresponding  value  when  the  velocity 
was  5  feet  per  second.  Since  the  pump  must  work  contin- 
ually against  this  head,  it  would  incur  a  financial  loss  that 
would  soon  exceed  the  extra  cost  of  installing  larger  pipes. 
It  is  found  in  plants  that  are  in  first  class  operation  that 
the  velocities  range  from  5  to  7  feet  per  second. 

The  calculations  in  Arts.  169  and  170  are  very  much 
simplified  by  the  use  of  the  chart  shown  in  the  Appendix. 
In  planning  a  system  of  this  kind,  find  the  friction  head 
on  the  pumps  and  the  diameters  of  the  pipes  for  various 
velocities,  say  4,  6,  8  and  10  feet  per  second.  Estimate  the 
probable  first  cost  and  the  depreciation  of  the  conduit  sys- 
tem for  each  velocity,  and  balance  these  figures  with  the 
operating  cost  for  a  period  of,  say  five  years,  to  see  which  is 
the  most  economical  velocity  to  use  in  figuring  the  system. 

171.  Service  Connections  are  usually  installed  from  30 
to  36  inches  below  the  surface  of  the  ground,  and  are  in- 
sulated in  some  form  of  box  conduit  which  compares  favor- 
ably with  that  of  the  main  conduit.  Service  branches  are 


304  HEATING  AND  VENTILATION 

l1/^-,  IM:-  and  2-inch  wrought  iron  pipe.  These  are  usually 
carried  to  the  building-  from  the  conduit  at  the  expense  of 
the  consumer.  Such  branch  conduits  are  not  drained  by 
tile  drains. 

172.  Total  Steam  Available  and  It.  t.  u.  Liberated  per 
Hour  for  Heating  the  Circulating  Water: — The  amount  of 
steam  available  for  heating-  the  circulating-  water  is  that 
given  off  by  the  generating  units,  plus  that  from  -the  cir- 
culating pumps,  plus  that  from  the  city  water  supply  pumps 
if  there  be  any,  plus  that  from  the  auxiliary  steam  units 
in  the  plant,  i.  e.,  small  pumps,  engines,  etc.  In  the  typical 
application  this  amounts  to  23100  +  12720  +  8680  —  44500 
pounds  per  hour. 

This  steam,  of  course,  is  not  equal  to  good  dry  steam  in 
heating  value  because  of  the  work  it  has  done  in  the  engine 
and  pump  cylinders,  but  a  good  estimate  of  its  value  may 
be  approximated.  In  addition  to  the  terms  used  in  Equation 
93,  let  q'  =  heat  in  the  returning  condensation  per  pound; 
then  the  heat  available  for  heating  purposes  per  pound  of 
exhaust  steam  is 

B.  t.  u.  =  xr  +  q  —  q'  (97) 

It  is  probably  safe  to  consider  the  quality  of  the  steam  as 
85  per  cent,  of  that  of  good  dry  steam  at  the  same  pressure. 
Since  the  pressure  of  the  exhaust  from  a  non-conde*nsing 
engine,  as  it  enters  the  heater,  is  near  that  of  the  atmos- 
phere, and  since  the  returning  condensation  is  at  a  tempera- 
ture of  about  180°,  the  total  amount  of  heat  given  off  from 
a  pound  of  exhaust  steam  to  the  circulating  water  is 
.85  X  970.4  +  180  —  (180  —  32)  =  856.84,  say  850.  If  W*  = 
pounds  of  exhaust  steam  available,  the  total  number  of 
B.  t.  u.  given  off  from  the  exhaust  steam  per  hour  is 

Total  B.  t.  u.  =  850  W,  (98) 

Applying  this  to  the  typical  power  plant  gives  850  X 
44500  =  37825000  B.  t.  u.  per  hour.  This  amount  is  probably 
a  maximum  under  the  conditions  of  lighting  units  as  stated, 
and  would  be  true  for  only  5  hours  out  of  24.  At  other 
times  the  exhaust  steam  drops  off  from  the  lighting  units 
and  this  deficiency  must  be  made  good  by  heating  the  circu- 
lating water  directly  from  the  coal,  by  passing  the  water 
through  heating  boilers  or  by  passing  it  through  economiz- 
ers where  it  is  heated  by  the  waste  heat  from  the  stack 


DISTRICT   HEATING  305 

i 

173.  Amount  of  Hot  Water  Radiation  in  the  District 
that  can  be  Supplied  by  One  Pound  of  Exhaust  Steam  on  a 
Zero  Day: — In  Art.  166,  each  pound  of  water  takes  on  25 
B.  t.  u.  in  passing-  through  the  reheaters  at  the  power  plant, 
and  gives  off  at  least  20  B.  t.  u.  in  passing-  through  the 
radiator.  The  number  of  pounds  of  water  heated  per  pound 
of  steam  per  hour  is,  Ww  =1  (Total  B.  t.  u.  available  per 
pound  of  exhaust  steam  per  hour)  -^  25,  and  the  total  radia- 
tion supplied  is 


Total  B.  t.  u.  available  per  Ib.  of  exhaust  steam  per  hr. 

Rw  =   -  —  (99) 

8.33    X    25 

which  for  average  practice  reduces  to 


850 

/'«<   =  —    —  =   4  square  feet  approx.  (100) 

208 


Applying'  Equation  99  for  the  five  hour  period  when  the 
exhaust  steam  is  maximum  gives  Rw  =  37825000  +  208  = 
181851  square  feet.  It  is  not  safe  to  figure  on  the  peak  load 
conditions.  It  is  better  to  assume  that  for  half  the  time, 
35000  pounds  of  steam  are  available  and  will  heat  35000  X 
4  =  140000  square  feet  of  radiation. 


174.  The  Amount  of  Circulating  Water  Passed  through 
the  Heater  Necessary  to  Condense  One  Pound  of  Exhaust 
Steam  is 

Total  B.  t.  u.  available  per  Ib.  of  exhaust  steam  per  hr. 
Ww  =  -  —(101) 

25 


With  the  value  given  above  for  the  exhaust  steam  this  be- 
comes, for  100  and  85  per  cent,  respectively, 

1000 

Ww  =  -    -  =   40  pounds  (102) 

25 

850 

Ww   — =  34  pounds  (103) 

25          « 


306  HEATING  AND   VENTILATION 

% 

175.  Amount    of    Hot   Water    Radiation   in    the    District 
that  can  be  Heated  by  One  Horse-Power  of  Exhaust  Steam 
from  a   Non-Condensing  Engine  on  a  Zero   Day: — 

Rw  =  4   X    (pounds  of  steam  per  H.  P.  hour)        (104) 
This  reduces  for  the  various  types  of  engines,  as  follows: 
Simple  high  speed  4    X    34   =    136  square  feet, 
medium   "      4    X    30    =    120 
Corliss  4    X    26    =    104 

Compound  high  "  4  X  26  =  104 
medium  "  4  X  25  =  100 
Corliss  4  X  22  =  88 

176.  Amount  of  Radiation  that  can  be   Supplied  by  Ex- 
haust  Steam  in  Equations  99  and  100  at  any  other  Temper- 
ature   of    the    Water,    t,r,    than   that    Stated,    with    the    HOOII.J 
Temperature,  t',  Remaining-  the  Same: — The  amount  of  heat 
passing  through  one  square  foot  of  the  radiator  to  the  room 
is  in  proportion  to  t,<?  —  /'.     In  Equations  99  and  100,  /.<•  —  t'  — 
100.     Now   if  tw   be  increased  x  degrees,   so   that   tw  —  /'    = 
(100  +  x)  then  each  square  foot  of  radiation  in  the  building 

100    +   x 

will    give    off    times    more    heat    than    before    and 

100 

each  pound  of  exhaust  steam  will  supply  only 

4    X    100 

Rw  =  —  —  square  feet  (105) 

100    +   x 

This  for  an  increase  of  30  degrees,  which  is  probably  a  max- 
imum, is 

4 

Rw   =  =   3  square  feet  (106) 

1.3 

Compared  with  Equation  100,  Equation  105  shows,  with  a 
high  temperature  of  the  water  entering  the  radiator,  that 
less  radiation  is  necessary  to  heat  any  one  room  and  that 
each  square  foot  of  surface  becomes  more  nearly  the  value 
of  an  equal  amount  of  steam  heating  surface.  Calculations 
for  radiation,  however,  are  seldom  made  from  high  tempera- 
tures of  the  water,  and  this  article  should  be  considered  an 
exceptional  case. 

177.  Exhaust   Steam  Condenser   (Reheater),  for  Reheat- 
ing   the    Circulating    "Water: — In    the    layout    of    any    plant 
the    reheaters    should    be    located    close    to    the    circulating 


DISTRICT  HEATING 


307 


pumps  on  the  high  pressure  side.  They  are  usually  of  the 
surface  condenser  type  (Fig.  167)  and  may  or  may  not  be 
installed  in  duplicate.  Of  the  two  types  shown  in  the  fig- 
ure, the  water  tube  type  is  probably  the  more  common.  The 
same  principles  hold  for  each  in  design.  In  ordinary  heaters 
for  feed  water  service,  wrought  iron  tubes  of  1%-  to  2-inches 


WATTR     3TTAM 


WATER-TUBE  TYPE 


Fig.  167. 


STEAM-TUBE  TYPE 


DRIP 


diameter  are  generally  used,  but  for  condenser  work  and 
where  a  rapid  heat  transmission  is  desired,  brass  or  copper 
tubes  are  used,  having  diameters  of  %-  to  1-inch.  In  heating 
the  circulating  water  for  district  service,  the  reheater  is 
doing  very  much  the  same  work  as  if  used  on  the  condens- 
ing system  for  engines  or  turbines.  The  chief  difference  is 
in  the  pressures  carried  on  the  steam  side,  the  reheater  con- 
densing the  steam  near  atmospheric  pressure  and  the  con- 
denser carrying  about  .9  of  a  perfect  vacuum.  In  either  case 
it  should  be  piped  on  the  water  side  for  water  inlet  and  out- 
let, while  the  steam  side  should  be  connected  to  the  exhaust 
line  from  the  engines  and  pumps,  and  should  have  proper 
drip  connection  to  draw  the  water  of  condensation  off  to  a 
condenser  pump.  This  condenser  pump  usually  delivers  the 
water  of  condensation  to  a  storage  tank  for  use  as  boiler 
feed,  or  for  use  in  making  up  the  supply  in  the  heating 
system. 

In  determining  the  details  of  the  condenser  the  follow- 
ing important  points  should  be  investigated:  the  amount  of 
heating  surface  in  the  tubes,  the  size  of  the  water  inlet  and 
outlet,  the  size  of  the  pipe  for  the  steam  connection,  the  size 
of  the  pipe  for  the  water  of  condensation  and  the  length 
and  cross  section  of  the  heater. 

178.     Amount  of  Heating  Surface  in  the  Reheater  Tubes: 

— The  general  equation  for  calculating  the  heating  surface  in 


308  HEATING  AND  VENTILATION 

the  tubes  of  a  reheater  (assuming  all  heating-  surface  on 
tubes  only),  is 

Total  B.  t.  u.  given  up  by  the  exhaust  steam  per  hr. 

Rt  =  (107) 

K  (Temp.  diff.  between  inside  and  outside  of  tubes) 

The  maximum  heat  given  off  from  one  pound  of  exhaust 
steam  in  condensing  at  atmospheric  pressure  is  1000  B.  t.  u., 
the  average  temperature  difference  is  approximately  47 
degrees,  and  K  may  be  taken  427  B.  t.  u.  per  degree  dif- 
ference per  hour.  In  determining  K,  it  is  not  an  easy  mat- 
ter to  obtain  a  value  that  will  be  true  for  average  practice. 
Carpenter's  H.  &  V.  B.  Art.  47  quotes  the  above  figure  for 
tests  upon  clean  tubes,  and  volumes  of  water  less  than 
1000  pounds  per  square  foot  of  heating  surface  per  hour. 
It  is  found,  however,  that  the  average  heater  or  condenser 
tube  with  its  lime  and  mud  deposit  will  reduce  the  efficiency 
as  low  as  40  to  50  per  cent,  of  the  maximum  transmission. 
Assume  this  value  to  be  45  per  cent.;  then  if  Ws  is  the 
number  of  pounds  available  exhaust  steam,  Equation  107 
becomes 

1000   Ws  1000  Ws  1000  TF.,          TF,, 

Rt  = -  (108) 

K(ts  —  tw)      427  X. 45X47  9031  9.1 

In  "Steam  Engine  Design,"  by  Whitham,  page  283,  the 
following  equation  is  given  for  surface  condensers  used  on 
shipboard: 

W  L 


8  = 


CK  <Ti  —  O 

where  8  =  tube  surface,  W  =  total  pounds  of  exhaust  steam 
to  be  condensed  per  hour,  L  =  latent  heat  of  saturated  steam 
at  a  temperature  Tlf  K  =  theoretical  transmission  of  B.  t.  u. 
per  hour  through  one  square  foot  of  surface  per  degree  dif- 
ference of  temperature  —  556.8  for  brass,  c  =  efficiency  of 
the  condensing  surface  —  .323  (quoted  from  Isherwood),  TI  = 
temperature  of  saturated  steam  in  the  condensers,  and  t  = 
average  temperature  of  the  circulating  water. 

With  L  =  970.4,  c  =  .323,  K  =   556.8  and  TI  —  t  =  47,  we 
may  state  the  equation  in  terms  of  our  text  as 

970.4  Ws  970.4  Ws         Ws 

Rt  = = =  (109) 

.323  X  556.8  X  47  8446  8.7 

In  Sutcliffe  "Steam  Power  and  Mill  Work,"  page  512,  the 
author  states  that  condenser  tubes  in  good  condition  and  set 


DISTRICT   HEATING  309 

in  the  ordinary  way  have  a  condensing-  power  equivalent  to 
13000  B.  t.  u.  per  square  foot  per  hour,  when  the  condensing 
water  is  supplied  at  60  degrees  and  rises  to  95  degrees  at  dis- 
charge, although  the  author  gives  his  opinion  that  a  trans- 
mission of  10000  B.  t.  u.  per  square  foot  per  hour  is  all  that 
should  be  expected.  This  checks  closely  with  Equation  108, 
which  gives  the  rate  of  transmission  9031  B.  t.  u.  per  square 
foot  per  hour. 

The  following  empirical  equation  for  the  amount  of  heat- 
ing surface  in  a  heater  is  sometimes  used: 

Rt  =  .0944  Ws  (110) 

where  the  terms  are  the  same  as  before. 

APPLICATION. — Let  the  total  amount  of  exhaust  steam 
available  for  heating  the  circulating  water  be  35000  pounds 
per  hour,  the  pressure  of  the  steam  in  the  condenser  be 
atmospheric  and  the  water  of  condensation  be  returned  at 
180°;  also,  let  the  circulating  water  enter  at  155°  and  be 
heated  to  180°.  These  values  are  good  average  conditions. 
The  assumption  that  the  pressure  within  the  condenser  is 
atmospheric  might  not  be  fulfilled  in  every  case,  but  can  be 
approached  very  closely.  From  these  assumptions  find  the 
square  feet  of  surface  in  the  tubes. 

35000 

Equation   108,  Rt    =   =    3846   sq.   ft. 

9.1 

35000 

Equation   109,  Rt    =   -   =    4023  sq.   ft. 

8.7 

Equation   110,  Rt    =    35000    X    .0944    =    3304   sq.   ft. 

1000  X  35000 

Sutcliffe  Rt    =  -  -  —   3500  sq.  ft. 

10000 

If  3846  square  feet  be  the  accepted  value  it  will  call  for 
three  heaters  having  1282  square  feet  of  tube  surface  each. 

179.  Amount  of  Reheater  Tube  Surface  per  Engine 
Horse-Power: — Let  ws  be  the  pounds  of  steam  used  per 
/.  H.  P.  of  the  engine;  then  from  Equation  108 

Ws 

Rt  (per  I.  H.  P.)   =  (111) 

9.1 


310  HEATING   AND  VENTILATION 

This  reduces  for  the  various  types  of  engines  as  follows: 

Simple   high   speed  34  —   9.1  =  3.74  square  feet 

medium      "  30  —    9.1  =  3.30 

Corliss  26  —    9.1  =  2.86 

Compound   high    "  26  —    9.1  =  2.86 

"       medium     "  25  —   9.1  =  2.75          "          " 

Corliss  22  -    9.1  =  2.42          "  "     . 

180.  Amount    of    Hot    Water   Radiation    in    the    District 
that  can  be  Supplied  by  One   Square  Foot  of  Reheater  Tube 
Surface: — If    the    transmission    through   one    square    foot    of 
tube  surface  be  K  (ts —  tw)  =  9031  B.  t.  u.  per  hour  and  the 
amount    of    heat    needed    per    square    foot    of    radiation    per 
hour  =  8.33   X   25  =  208,  as  given  in  Eqaution  99,  then 

9031 

Rw  (per  sq.  ft.  of  tube  surface)   =  -    -  =   43.4  sq.  ft.      (112) 

208 

181.  Some  Important   Reheater   Details: — Inlet  and  outlet 
pipes. — Having  three  heaters  in  the  plant,   it  seems   reason- 
able that  each  heater  should  be  prepared  for  at  least  one- 
third    of   the    water    credited    to   the    exhaust    steam.      From 
Art.  173  this  is  140000  -f-   3   =   46667  gallons  =   10800000  cubic 
inches    per  hour.      The   velocity   of    the   water   entering   and 
leaving  the  heater  may  vary  a  great  deal,  but  good  values 
for    calculations    may    be    taken    between    5    and    7    feet    per 
second.     Assuming  the  first  value   given,   we  have   the   area 
of  the  pipe  =  10800000  -j-  (5  X  12  X  3600)  =  50  square  inches, 
and  the  diameter  8  inches. 

The  size  of  the  reJieater  shell, — Concerning  the  velocity  of 
the  water  in  the  reheater  itself,  there  may  be  differences  of 
opinion;  100  feet  per  minute  will  be  a  good  value  to  use 
unless  this  value  makes  the  length  of  the  tube  too  great  for 
its  diameter.  If  this  is  the  case  the  tube  will  bend  from 
expansion  and  from  its  own  weight.  At  this  velocity  the 
free  cross  sectional  area  of  the  tubes,  assuming  the  water 
to  pass  through  the  tubes  as  in  Fig.  167,  will  be  150  square 
inches.  If  the  tubes  be  taken  %  inch  outside  diameter, 
with  a  thickness  of  17  B.  W.  G.,  and  arranged  as  usual  in 
such  work,  it  will  require  about  475  tubes  and  a  shell  diam- 
eter of  approximately  30  inches.  If  the  inner  surface  of  the 
tube  be  taken  as  a  measurement  of  the  heating  surface  and 


DISTRICT  HEATING  311 

the  total  surface  be  1282  square  feet,  the  length  of  the  re- 
heater  tubes  will  be  approximately  16  feet. 

The  ratio  of  the  length  of  the  tube  to  the  diameter  is, 
in  this  case,  256,  about  twice  as  much  as  the  maximum  ratio 
used  by  some  manufacturers.  It  will  be  better,  therefore, 
to  increase  the  number  of  tubes  and  decrease  the  length. 
With  a  velocity  of  the  water  of  50  feet  per  minute,  the 
values  will  be  approximately  as  follows:  free  cross  sec- 
tional area  of  the  tubes,  300  square  inches;  number  of  tubes, 
950;  diameter  of  shell,  40  inches;  length  of  tubes,  8  feet. 
These  values  check  fairly  well  and  could  be  used. 

The  size  of  exhaust  steam  connection.  —  To  calculate  this,  use 
the  equation 

144  Qs 

A  =  -  (113) 

V 

where  Qs  =  volume  of  steam  in  cubic  feet  per  minute,  V  = 
velocity  in  feet  per  minute,  and  A  =  area  of  pipe  in  square 
inches.  When  applied  to  the  reheater  using  35000  pounds 
of  steam  per  hour,  at  26  cubic  feet  per  pound  and  at  a  veloc- 
ity through  the  exhaust  pipe  of  6000  feet  per  minute,  it  gives 

144  X  35000  X  26 

A  =  -  =  360  sq.  in.   =   22  in.  dia. 
60  X  6000 

Try  also,  from  Carpenter's  H.  &  V.  B.,  page  284 


d  =  V  -  (114) 

1.23 

Allowing  30  pounds  of  steam  per  H.  P.  hour  for  non-condens- 
ing engines  we  have  35000  -=-  30  =  1166  horse-power;  then 
applying  the  above  we  obtain  d  =  16  inches.  Comparing 
the  two  Equations,  113  and  114,  the  first  will  probably  admit 
of  a  more  general  application.  The  velocity  6000  for  exhaust 
steam  may  be  increased  to  8000  for  very  large  pipes  and 
should  be  reduced  to  4000  for  small  pipes.  In  the  above 
applications  a  20  inch  pipe  will  suffice. 

The  return  pipe  for  condensation.  —  The  diameter  of  the  pipe 
leading  to  the  condenser  pump  will  naturally  be  taken  from 
the  catalog  size  of  the  pump  installed.  This  pump  would 
be  selected  from  capacities  as  guaranteed  by  the  respective 
manufacturers  and  should  easily  be  capable  of  handling  the 
amount  of  water  that  is  condensed  per  hour. 

The  value  of  a  high  pressure  steam  connection.  —  If  desired, 
the  reheater  may  also  be  provided  with  a  high  pressure 


312 


HEATING  AND  VENTILATION 


steam  connection,  to  be  used  when  the  exhaust  steam  is  not 
sufficient.  This  steam  is  then  used  through  a  pressure-re- 
ducing valve  which  admits  the  steam  at  pressures  varying 
from  atmospheric  to  5  pounds  gage.  There  is  some  question 
concerning  the  advisability  of  doing  this.  Some  prefer  to 
install  a  high  pressure  steam  heater,  as  in  Art.  182,  to  be 
used  independently  of  the  exhaust  steam  heaters.  This 
removes  all  possibility  of  having  excessive  back  pressure 
on  the  engine  piston,  as  is  sometimes  the  case  where  high 
pressure  steam  is  admitted  with  the  exhaust  steam. 

It  has  been  the  experience  of  some  who  have  operated 
such  plants  that  where  more  heat  is  needed  than  can  be 
supplied  by  the  exhaust  steam,  it  is  better  to  resort  to  heat- 
ing boilers  and  economizers  ,than  to  use  high  pressure  steam 
for  heating. 

182.  High  Pressure  Steam  Heater: — When  this  heater  is 
used  it  is  located  above  the  boiler  so  that  all  the  condensa- 


Fig.  168. 

tion  freely  drains  back  to  the  boilers  by  gravity  as  in  Fig. 
168.     In  calculating  the  tube  surface,  use  Equation  107  with 


DISTRICT   HEATING  313 

the  full  value  of  the  steam  and  the  steam  temperatures 
changed  to  suit  the  increased  pressure.  Such  a  heater  as 
this  gives  good  results. 

183.  Circulating  Pumps: — Two  types  of  pumps  are  in 
general  use:  centrifugal  and  reciprocating.  Each  type  is 
somewhat  limited  in  its  operation.  The  centrifugal  pump 
has  difficulty  in  operating  against  high  heads  and  the  recip- 
rocating pump  is  very  noisy  when  running  at  a  high  piston 
speed.  Since  each  type  is  in  successful  operation  in  many 
plants,  no  comparisons  will  be  made  between  them  further 
than  to  say  that  the  former,  being  operated  by  a  steam  en- 
gine, may  be  run  more  economically  than  the  latter  because 
of  the  possibilities  of  using  the  steam  expansively.  It  will 
be  noted,  however,  that  this  same  steam  is  to  be  used  in  the 
exhaust  steam  heaters  for  warming  the  circulating  water 
and  hence  there  would  be  little,  if  any,  direct  loss  from  this 
source  in  the  use  of  the  reciprocating  pump. 

Having  given  the  maximum  amount  of  water  to  be 
circulated  per  hour,  consult  trade  catalogs  and  select  the 
number  of  pumps  and  the  size  of  each  pump  to  be  installed. 
The  sizes  of  the  pumps  can.  easily  be  determined  when  the 
number  of  them  has  been  decided  upon.  This  latter  point 
is  one  upon  which  a  difference  of  opinion  will  probably  be 
found.  No  exact  rule  can  be  applied.  In  a  plant  of,  say 
not  more  than  150000  square  feet  of  radiation  (150000  gal- 
lons of  water  per  hour,  or  3  million  gallons  for  twenty-four 
hours),  some  designers  would  put  in  three  pumps,  each 
having  1.5  million  gallons  capacity;  in  which  case  one  pump 
could  be  cut  out  for  repairs  and  the  other  two  would  be 
able  to  care  for  the  service  temporarily.  Other  designers 
would  use  four  pumps  at  about  one  million' gallons  each. 
The  fewer  the  pumps  installed,  in  any  case,  the  greater 
should  be  the  capacity  of  each.  The  following  values  will 
be  found  fairly  satisfactory: 

1  Pump.  Cap.   =   (1  to  1.25)  times  max.  requirem't  of  system 

2  Pumps.   "     (each)    =   .75         " 

3  Pumps.   "         "          =   .5 

4  Pumps.   "          "          rr   .3 

Having  given  the  capacity  of  each  pump  in  gallons  of 
water  per  minute,  the  size,  the  horse-power  and  the  steam 
consumption  of  each  pump  can  be  calculated.  In  obtaining 
the  size  of  the  pump  it  will  be  necessary  to  know  the 


314  HEATING  AND  VENTILATION 

V,  of  the  piston  in  feet  per  minute,  the  strokes,  N,  per  minute 
and  the  per  cent,  of  sli<p,  n  (100  per  cent.  —  8,  where  8  =  hy- 
draulic efficiency).  The  speed  varies  between  100,  for  small 
pumps,  and  75,  for  large  pumps.  The  strokes  vary  between 
200,  for  small  pumps,  and  10,  for  large  pumps,  and  the  slip 
varies  between  5  and  40  per  cent.,  depending-  upon  the  fit  of 
the  piston  and  the  valves.  In  pumps  that  have  been  in  serv- 
ice for  some  time  the  slip  will  probably  average  20  per  cent. 
The  cross  sectional  area  of  the  water  cylinder  in  square 
inches  is 

cubic  inches  pumped  per  minute 

TF.  C.  A.   =  -  (.15) 

8    X    V    X    12 

from  which  we  may  obtain  the   diameter  of  the  water  cyl- 
inder. 

The  steam  cylinder  area  is  usually  figured  as  a  certain 
ratio  to  that  of  the  water  cylinder  area,  as 

8.  C.  A.    =    (1.5  to  2.5)    X    B7.  C.  A  (116) 

from  which  we  may  obtain  the  diameter  of  the  steam  cylin- 
der. 

The  length  of  the  stroke,  L,  in  inches,  may  be  obtained 
from  the  speed  and  the  number  of  strokes  such  that 

12   V 
L  =  (117) 

N 

All  direct  acting  steam  pumps  are  designated  by  diam- 
eter of  steam  cylinder  x  diameter  of  water  cylinder  X  length 
of  stroke,  as 

14"   X    12"   X    18" 

Duplex  pumps  have  twice  the  capacity  of  single  pumps 
having  the  same  sized  cylinders. 

To  find  the  indicated  horse-power,  /.  II.  P.,  of  the  pumps, 
reduce  the  pressure  head,  p,  in  pounds  per  square  inch,  to 
pressure  head  in  feet,  li\  multiply  this  by  the  pounds  of 
water,  W,  pumped  per  minute  and  divide  the  product  by 
33000  times  the  mechanical  efficiency,  E. 

w  n 

/.  H.  P.   =  (118) 

33000  E 

To  reduce  from  pressure  head  in  pounds  to  pressure 
head  in  feet,  divide  the  pressure  head  in  pounds  by  weight 


DISTRICT    HEATING  315 

of  a  column  of  water  one  square  inch  in  area  and  one  foot 
hig-h.     The  general  equation  for  this  is 

144  p 


h  - 


where  w  =  the  weight  of  a  cubic  foot  of  water  at  the  given 
temperature  and  p  r=  differential  pressure  in  pounds  per 
square  inch. 

In  pump  service  of  this  kind  the  pressure  head,  p, 
against  which  the  pump  is  acting,  is  not  the  result  of  the 
static  head  of  water  in  the  system  but  is  due  to  the  inertia 
of  the  water  and  to  the  resistance  to  the  flow  of  water 
through  the  piping  system  and  the  heaters.  This  frictional 
resistance  may  be  calculated  as  shown  in  Art.  169.  Read 
this  part  of  the  work  over  carefully. 

For  an  illustration  of  combined  pressure  head,  p,  and 
friction  head,  hf,  see  Art.  186  on  boiler  feed  pumps.  Having 
found  the  /.  H.  P.  of  any  pump,  multiply  it  by  the  steam  con- 
sumption per  7.  77.  P.  hour  and  the  result  will  be  the  steam 
consumption  of  the  pump.  This  exhaust  steam  will  be  con- 
sidered a  part  of  the  general  supply  when  figuring  the  size 
of  the  exhaust  steam  heaters  in  the  system. 

The  mechanical  efficiency,  E,  of  piston  pumps  depends 
upon  the  condition  of  the  valves  and  upon  the  speed,  and 
varies  from  90  per  cent,  in  new  pumps,  to  50  per  cent,  in 
pumps  that  are  badly  worn.  A  fair  average  would  be  70 
per  cent. 

The  steam  consumption  for  reciprocating,  simple  and 
duplex  non-condensing  pumps  would  approximate  100  to 
200  pounds  of  steam  per  7.  77.  P.  hour — the  greater  values  re- 
ferring to  the  slower  speeds. 

184.  Centrifugal  Pumps: — Centrifugal  pumps  are  of 
two  classifications,  the  Volute  and  the  Turbine.  The  prin- 
ciples upon  which  each  operate  are  very  similar.  The  ro- 
tating impeller,  or  rotor,  with  curved  blades  draws  the 
water  in  at  the  center  of  the  pump  and  delivers  it  from  the 
circumference.  The  rotor  is  enclosed  by  a  cast  iron  case- 
ment which  is  shaped  more  or  less  to  fit  the  curvature  of 
the  edges  of  the  blades  on  the  rotor.  Centrifugal  pumps 
are  used  where  large  volumes  of  water  are  required  at  low 
heads.  They  are  used  in  city  water  supply  systems,  in  cen- 
tral station  heating  systems,  in  condenser  service,  in  irri- 


316  HEATING  AND  VENTILATION 

gation  work  and  in  many  other  places  where  the  pressure 
head  operated  against  is  not  excessive.  The  efficiency  of 
the  average  centrifugal  pump  is  from  65  to  80  per  cent., 
75  per  cent,  being  not  uncommon.  In  places  where  such 
pumps  are  used  the  head  is  usually  below  75  feet,  although 
some  types,  when  direct  connected  to  high  speed  motors, 
are  capable  of  operating  against  heads  of  several  hundred 
feet. 

Some  of  the  advantages  of  centrifugal  pumps  over  hor- 
izontal reciprocating  pumps  are:  low  first  cost,  simplicity, 
few  moving  parts,  compactness,  uniform  flow  and  pressure 
of  water,  freedom  from  shock,  possibilities  of  direct  connec- 
tion to  high  speed  motors  and  the  ability  to  handle  dirty 
water  without  injuring  the  pump. 

One  of  the  advantages  of  piston  pumps  over  centrifugal 
pumps  is  the  fact  that  they  are  more  positive  in  their  opera- 
tion and  work  against  higher  heads. 

Centrifugal  pumps,  when  connected  to  engine  and  tur- 
bine drives,  benefit  by  the  expansion  of  the  steam  and  are 
much  more  economical  than  the  direct  acting  piston  pump, 
which  takes  steam  at  full  pressure  for  nearly  the  entire 
stroke.  The  amount  of  steam  used  in  the  pumps  in  central 
station  work,  however,  is  not  a  serious  factor,  since  all  of 
the  heat  in  the  steam  that  is  not  used  in  propelling  the 
water  through  the  mains  is  used  in  the  heaters  to  increase 
the  temperature  of  the  water. 

The  sphere  of  usefulness  of  the  centrifugal  pump  in 
central  station  heating  is  increasing.  The  direct  acting 
piston  pump,  when  operating  at  fairly  high  speeds,  causes 
hammering  and  pounding  in  the  transmission  lines,  and 
these  noises  are  sometimes  conveyed  to  the  residences  and 
become  annoying  to  the  occupants.  This  feature  is  not  so 
noticeable  in  the  operation  of  the  centrifugal  pump. 

APPLICATION. — In  Art.  167  assume  the  capacity  of  the 
plant,  10  business  blocks  and  21  residence  blocks,  to  require 
184500  gallons  of  water  per  hour;  the  same  to  be  pumped 
against  a  pressure  head  (Art.  169)  of  50 — 5  pounds,  by  hori- 
zontal, direct  acting  piston  pumps.  Assume  also  the  steam 
consumption  of  the  pumps  to  be  100  pounds  per  /.  H.  P.  hour 
and  the  average  temperature  of  the  water  at  the  pumps  to 
be  (180  +  155)  -f-  2  =  167.5  degrees.  Apply  Equation  118, 
where  li  =  calculated  total  friction  head  for  the  longest  line 


DISTRICT   HEATING  317 

in  the  system  (this  is  designated  by  Jif  in  Art.  169),  or  where 
p  =  total  difference  between  the  incoming-  and  the  outgoing 
pressures.  With  the  weight  of  a  cubic  foot  of  water  at  167.5 
degrees  =  60.87  pounds  and  with  p  =  45,  we  have  h  =  106.5 
feet,  and  the  indicated  horse-power  of  the  pumps,  assuming 
65  per  cent,  mechanical  efficiency,  is 

184500  X  8.33  X  106.5 

/.  H.  P.   -  -  — •  =   127.2 

33000  X  .65  X  60 

From  this  the  steam  consumption  will  probably  be  12720 
pounds  per  hour. 

If  centrifugal  pumps  were  selected  the  horse-power 
would  be  calculated  from  the  same  equation,  but  the  steam 
consumption  of  the  engine  driving  it  would  probably  be  30 
to  40  pounds  of  steam  per  horse-power. 

185.  City  Water  Supply  Pumps: — Horizontal,  direct  act- 
ing duplex  pumps  for  use  on  city  water  supply  service  are 
the  same  as  those  used  to  circulate  the  water  in  heating 
systems;  hence,  the  foregoing  descriptions  apply  here.  The 
/.  H.  P.  of  the  city  water  supply  pumps  would  be  calculated 
by  use  of  Equation  118.  If  the  pumps  lift  the  water  from  the 
wells,  as  would  probably  be  the  case,  the  suction  pressure 
would  be  negative  and  would  be  added  to  the  force  pressure. 

APPLICATION. — Assume  the  pressure  in  the  fresh  water 
mains  60  pounds  and  the  suction  pressure  10  pounds;  there- 
fore, p  =  60  —  ( — 10)  =  70  pounds,  and  with  the  water  at 
65  degrees,  h  =  144  X  70  -=-  62.5  =  161  feet.  These  pumps 
are  each  rated  at  1.5  million  gallons  in  24  hours,  and  deliver 
62500  X  8.33  =  520833  pounds  of  water  per  hour,  when  run- 
ning at  full  capacity.  Assuming  each  pump  to  deliver  75  per 
cent,  of  the  full  requirement  of  the  system,  the  total  amount 
of  water  pumped  per  hour  for  the  city  water  supply  would 
approximate  520833  -h  .75  =  694444  pounds,  and  the  total 
average  horse-power  used  in  pumping  the  water  would  be 

694444  X  161 

/.  H.  P.  =  rr   86.8 

60  X  33000  X  .65 

With  100  pounds  of  steam  per  horse-power  hour,  this  would 
amount  to  8680  pounds  of  exhaust  steam  available  per  hour 
for  use  in  heating  the  circulating  water. 

,  186.  Boiler  Feed  Pumps: — Horizontal  pumps  for  high 
pressure  boiler  feeding  are  selected  in  a  similar  way.  Such 
units  are  called  auxiliary  steam  units  and,  because  the  steam 


318  HEATING  AND  VENTILATION 

required  is  small,  they  are  sometimes  piped  to  a  feed  water 
heater  for  heating-  the  boiler  feed.  The  velocity  of  the  water 
through  the  suction  pipe  may  be  taken  200  feet  per  minute 
and  in  the  delivery  pipe  300  feet  per  minute.  The  piston 
speed,  the  strokes  per  minute  and  the  slip  would  be  very 
much  the  same  as  stated  under  circulating  pumps.  Such 
pumps  should  have  a  pumping-  capacity  about  twice  as  great 
as  the  actual  boiler  requirements,  and  in  small  plants  where 
only  one  pump  is  needed,  the  installation  should  be  in  dupli- 
cate. The  sizes  of  the  cylinders  and  the  efficiencies  are 
about  as  stated  for  the  larger  circulating  pumps. 

In  determining-  the  horse-power  of  a  boiler  feed  pump, 
four  resistances  must  be  overcome;  i.  e.,  pressure  head,  p,  or 
boiler  pressure;  suction  heat,  Its',  delivery  head,  7ia,  and 
the  friction  head,  hf.  The  first  three  values  are  usually 
given.  The  friction  head  includes  the  resistances  in  all  pip- 
ing-, ells  and  valves  from  the  supply  to  the  boiler.  The  fric- 
tion in  the  piping  may  be  taken  from  Table  42,  Appendix,  or 
it  may  be  worked  out  by  Equation  95.  The  friction  in  the  ells 
and  valves  is  more  difficult  to  determine  and  is  usually  stated 
in  equivalent  length  of  straight  pipe  of  the  same  diameter. 
A  rough  rule  used  by  some  in  such  cases  is  as  follows:  "to 
the  length  of  the  given  pipe,  add  60  times  the  nominal  diam- 
eter of  the  pipe  for  each  ell,  and  90  times  the  diameter  for 
each  globe  valve,"  then  find  the  friction  head  as  stated 
above.  A  straight  flow  gate  or  water  valve  could  safely  be 
taken  as  an  ell.  For  simplicity  of  calculation,  all  of  the 
above  resistances  may  be  reduced  to  an  equivalent  head, 
such  that 

(119) 
144p 

lie  =  •  +  Jid  +  lis  +  IK 

w 

where  w  =  weight  of  one  cubic  foot  of  water  at  the  suc- 
tion temperature,  w  may  be  obtained  from  Table  9,  Ap- 
pendix, and  hf  may  be  taken  from  Table  42.  The  horse-power 
by  Equation  118  then  becomes,  if  W  —  pounds  of  water 
pumped  per  minute, 

TT  X  lie 

r.  n.  p. .  (120) 

330007? 

APPLICATION. — Let  p  =  125  pounds  gage,  tr  =  62.5,  7ia  —  8 
feet,  hn  —  20  feet,  horizontal  run  of  pipe  from  supply  to 


DISTRICT   HEATING  319 

pump  =  20  feet,  horizontal  run  of  pipe  from  pump  to  boiler  = 
30  feet;  also,  let  the  pump  supply  89000  pounds  of  water 
per  hour  to  the  boiler.  This  is  twice  the  capacity  of  the 
boiler  plant.  With  this  amount  of  water  at  the  usual  veloc- 
ity it  will  give  a  suction  pipe  of  4.5  inches  diameter,  and  a 
flow  pipe  of  4  inches  diameter.  Let  there  be  two  ells  and 
one  gate  valve  on  the  suction  pipe,  and  three  ells,  one  globe 
valve  and  one  check  valve  on  the  delivery  pipe.  We  then 
have  an  equivalent  of  107  feet  of  suction  pipe,  and  158  feet 
of  delivery  pipe.  Referring  to  Table  42,  Jtf  is  approximately 
7  feet,  and  the  total  head  is 

144  X  125 

lie  -  — •  +  8  +  20  +  7  =  323  feet. 

62.5 

In  the  use  of  most  boiler  feed  pumps  it  is  considered 
unnecessary  to  determine  hf  so  carefully.  A  very  satisfac- 
tory way  is  to  obtain  the  total  head  pumped  against,  exclu- 
sive of  the  friction  head,  and  add  to  it  5  to  15  per  cent.,  de- 
pending" upon  the  complications  in  the  circuit.  Substituting' 
the  above  in  Equation  120,  we  obtain 

89000  X  323 

/.  H.  P.  =  =  22.3 

60  X  33000  X  .65 

Work  out  the  value  of  hf  by  Equation  95  and  see  how 
nearly  it  checks  with  the  above. 

187.  Boilers: — A  number  of  boilers  will  necessarily  be 
installed  in  a  plant  of  this  kind,  and  a  g'ood  arrangement  is 
to  have  them  so  piped  with  water  and  steam  headers  that 
any  number  of  the  boilers  may  be  used  for  steaming  pur- 
ppses  and  the  rest  as  water  heaters.  They  should  also  be  so 
arranged  that  any  of  the  boilers  may  be  thrown  out  of 
service  for  cleaning  or  repairs  and  still  carry  on  the  work 
of  the  plant.  By  doing  this  the  boiler  plant  becomes  very 
flexible  and  each  boiler  is  an  independent  unit.  Any  good 
water  tube  boiler  would  serve  the  purpose  both  as  a  steam- 
ing- and  as  a  heating  boiler.  Where  the  boilers  are  used  as 
heaters,  the  water  should  enter  at  the  bottom  and  come  out 
at  the  top.  Where  the  water  enters  at  the  top  and  comes 
out  at  the  bottom,  the  excessive  heating  of  the  front  row  of 
tubes  retards  the  circulation  of  the  water  by  this  heat,  and 
produces  a  rapid  circulation  through  the  rear  tubes  where 
the  heat  is  the  least.  This  rapid  circulation  in  the  rear  tubes 


320  HEATING  AND  VENTILATION 

is  not  a  detriment,  but  it  is  less  needed  there  than  in  the 
front  ones.  It  would  be  decidedly  better  if  the  rapid  circu- 
lation were  in  the  front  row,  causing  the  heat  from  the  fire 
to  be  carried  off  more  readily,  and  by  this  means  giving  less 
danger  of  burning  the  tubes.  In  the  latter  case  the  forced 
circulation  from  the  pumps  will  be  aided  by  the  natural  cir- 
culation from  the  heat  of  the  fire,  and  the  life  of  all  the 
tubes  becomes  more  uniform.  Fig.  169  shows  a  typical 
header  arrangement. 

Boilers  are  usually  classified  as  fire  tube  and  water  tube. 
Fire  tube  boilers  are  of  the  multitubular  type,  having  the  flue 
gases  passing  through  the  tubes  and  water  surrounding 
them.  Water  tube  boilers  have  the  water  passing  through  the 
tubes  and  the  flue  gases  surrounding  them.  The  heating  sur- 
face of  a  boiler  is  composed  of  those  boiler  plates  having  the 
heated  flue  gases  on  one  side  and  the  water  on  the  other.  A 
boiler  horsc-potver  may  be  taken  as  follows: 
Centennial  Rating. 

One  B.  H.  P.   —  30  pounds  of  water  evaporated  from  feed 
water  at  100°  F.  to  steam  at  70  pounds  gage  pressure. 
A.  S.  M.  E. 

One  B.  H.  P.  =  34.5  pounds  of  water  evaporated  from 
and  at  212°  F. 

In  laying  out  a  boiler  plant  some  good  approximations 
for  the  essential  details  are: 

One  B.  H.  P.  —   11.5  square  feet  of  heating  surface, 
(multitubular  type). 

One  B.  H.  P.  r=  10  square  feet  of  heating  surface 
(water  tube  type). 

One  B.  H.  P.  •=.  .33  square  foot  of  grate  surface 
(small  plant,  say  one  boiler). 

One  J5.  H.  P.  =  .25  square  foot  of  grate  surface 
(medium  sized  plant,  say  500  H.  P.). 

One  B.  H.  P.  =  .20  square  foot  of  grate  surface 
(large  plants). 

Pounds  of  water  evaporated  per  square  foot  of  heating 
surface  per  hour  =  3  (approx.  value). 

188.  Square  Feet  of  Hot  Water  Radiation  that  can  be 
Supplied  on  a  Zero  Day  by  One  Boiler  Horse-Power  when  the 
Boiler  is  Used  as  a  Heater: — Assuming  that  the  coal  used  in 
the  plant  has  a  heating  value  of  13000  B.  t.  u.  per  pound, 


DISTRICT  HEATING  321 

and  that  the  efficiency  of  the  boiler  is  60  per  cent.,  each 
pound  of  coal  will  transmit  to  the  water  7800  B.  t.  u.  Sincv. 
each  pound  of  water  takes  up  25  B.  t.  u.  on  its  passage 
through  the  heating  boiler,  one  pound  of  coal  will  heat  312 
pounds,  or  37.5  gallons  of  water.  This  is  equivalent  to  sup- 
plying heat,  under  extreme  conditions  of  heat  loss,  to  37.5 
square  feet  of  radiation  for  one  hour.  One  boiler  horse- 
power, according  to  Art.  187,  is  equivalent  to  the  expendi- 
ture of  970.4  X  34.5  =  33478  B.  t.  u.  Now  since  each  pound 
of  coal  transfers  to  the  water  7800  B.  t.  u.,  one  boiler  horse- 
power will  require  33478  -f-  7800  =  4.29  pounds  of  coal.  If, 
then,  the  burning  of  one  pound  of  coal  will  supply  37.5 
square  feet  of  hot  water  radiation  for  one  hour,  one  boiler 
horse-power  will  supply  4.29  X  37.5  —  160  square  feet  for 
one  hour,  and  a  100  H.  P.  boiler  will  supply  16000  square  feet 
of  water  radiation  in  the  district  for  the  same  time.  These 
figures  have  reference  to  boilers  under  good  working  condi- 
tions and  probably  give  average  results. 

189.  Square  Feet  of  Hot  Water  Radiation  in  the  District 
that  can  be  Supplied  on  a.  Zero  Day  by  an  Economizer  Lo- 
cated in  the  Stack  Gases  between  the  Boilers  and  the  Chim- 
ney:— In  order  to  make  this  estimate  it  is  necessary  first  to 
know  the  horse-power  of  the  boilers,  the  amount  of  coal 
burned  per  hour,  the  pounds  of  gases  passing  through  the 
furnace  per  hour  and  the  heat  given  off  from  these  gases 
to  the  circulating  water  through  the  tubes. 

APPLICATION. — Let  C  =  pounds  of  coal  burned  per  hour  — 
boiler  horse-power  X  pounds  of  coal  per  boiler  horse-power 
hour,  Wa  =  pounds  of  air  passed  through  the  furnace  per 
pound  of  fuel  burned,  s  =  specific  heat  of  the  gases,  tb  — 
temperature  of  gases  leaving  boiler,  ts  =  temperature  of 
gases  leaving  economizer,  tw  —  temperature  of  water  enter- 
ing economizer  and  tf  =  temperature  of  water  leaving  the 
economizer.  Then,  if  8.33  pounds  of  water  will  supply  one 
square  foot  of  radiation  for  one  hour  we  have 

*  X  (C  X  Wa  +  C)  X  (tb  —  ts) 

R*   =  (121) 

8.33  X   (tf  —  tw) 

In  the  illustrative  plant,  44500  pounds  of  steam  per  hour 
are  generated  in  the  steam  boiler  plant  at  a  pressure  of  125 
pounds  gage.  To  find  the  boiler  horse-power  let  the  total 
heat  of  the  steam,  above  32°  at  125  pounds  gage,  be  1192 
B.  t.  u.,  and  let  the  temperature  of  the  incoming  feed  water 


322  HEATING  AND    VENTILATION 

to  the  boilers  be  60  degrees.  (In  most  cases  the  feed  water 
will  be  at  a  higher  temperature,  but  since  it  will  occasionally 
be  as  low  as  60  degrees,  this  value  should  be  used.)  The 
heat  put  into  a  pound  of  steam  under  these  conditions  is 
1192  —  (60  —  32)  =  1164  B.  t.  u.,  and  in  44500  pounds  it  will 
be  51798000  B.  t.  u.  Since  one  horse-power  of  boiler  service 
is  equivalent  to  33455  B.  t.  u.,  we  will  need  51798000  -=- 
33478  =  1548  boiler  horse-power.  This  horse-power  will 
take  care  of  all  the  engines  and  pumps  in  the  plant.  If  the 
coal  used  contains  13000  B.  t.  u.  per  pound  and  the  boilers 
have  60  per  cent,  efficiency,  7800  B.  t.  u.  will  be  given  to  the 
water  per  pound  of  fuel  burned,  and  the  amount  of  coal 
burned  per  hour  will  be  51798000  -=-  7800  =  6640  pounds. 
This  gives  6640  -=-  1548  =  4.3  pounds  of  fuel  per  boiler  horse- 
power hour,  and  6.7  pounds  of  water  evaporated  per  pound 
of  fuel.  If  the  flue  gases  have  12  per  cent.  CO2,  there  are 
used  according  to  experimental  data,  about  21  pounds  of  air 
or  22  pounds  of  the  gases  of  combustion,  per  pound  of  fuel 
burned.  This  is  equivalent  to  6640  X  22  =  146080  pounds  of 
flue  gases  total.  Suppose  now  that  these  gases  leave  the 
furnace  for  the  chimney  at  a  temperature  of  550  degrees  F., 
that  the  economizer  drops  the  temperature  of  the  gases 
down  to  350  degrees  (a  condition  which  is  very  reasonable) 
and  that  the  specific  heat  of  the  gases  is  about  .22,  we  have 
146080  X  .22  X  (550  —  350)  =  6427520  B.  t.  u.  given  off  from 
the  gases  per  hour  in  passing  through  the  economizer  (see 
numerator  in  Equation  121).  This  heat  is  taken  up  by  the 
circulating  water  in  passing  through  the  economizer  toward 
the  outgoing  main.  Now  if  the  water  as  it  returns  from  the 
circulating  system,  enters  the  economizer  at  155  degrees, 
and  leaves  at  180  degrees,  we  will  have  6427520  -^  (180  — 
155)  =  257100  pounds  of  water  heated  per  hour.  This  is 
equivalent  to  supplying  257100  4-  8.33  =  30864  square  feet  of 
radiation  per  hour  when  the  plant  is  running  at  its  peak 
load.  Taking  the  "pounds  of  steam  per  hour"  in  the  above 
as  the  only  variable  quantity,  we  are  fairly  safe  in  saying 
that  the  heat  in  the  chimney  gases  from  one  horse-power  of 
steaming  boiler  service  will  supply,  through  an  economizer, 
30864  4-  1548  —  20  square  feet  of  radiation  in  the  district. 
In  plants  where  only  7  pounds  of  water  are  allowed  to  each 
square  foot  of  radiation  per  hour,  this  becomes.  23. 8  square 
feet  of  radiation  instead. 


DISTRICT   HEATING  323 

100.  Square  Feet  of  Economizer  Surface  Required  to 
Heat  the  Circulating  Water  in  Art.  189:  —  Let  A"  =  the  coeffi- 
cient of  heat  transmission  through  clean  cast  iron  tubes  and 
E  rr  the  efficiency  of  the  tube  surface  when  in  average  serv- 
ice, also  let  the  terms  for  the  temperatures  of  the  gases  and 
the  circulating-  water  be  as  given  in  Art.  189,  then 

Heat  trans,  per  hour  from  gases  to  water 


Re  - 


K  X  E  X     ' 


(       t»   +   t.  tf 

\ 2~  ~ 


This  equation  assumes  that  the  rate  of  heat  flow  through 
the  tubes  is  the  same  at  all  points.  As  a  matter  of  fact  this 
rate  changes  slightly  as  the  water  becomes  heated,  but  the 
error  is  not  serious  in  an  equation,  where  the  efficiency  of 
the  surface  may  be  anything  from  100  per  cent,  in  new  tubes 
to  as  low  as  30  to  40  per  cent,  for  old  ones. 

APPLICATION. — Let  K  —   7  and  E  —   .4,  then 

6427520 
Re  -  =   8125  sq.  ft. 

(550  +  350          180  +  155  \ 
I 
2                            2  / 

With  12  square  feet  of  surface  per  tube  this  gives  677  tubes. 

101.  Square  Feet  of  Economizer  Surface  to  Install  when 
the  Economizer  is  to  be  Used  to  Heat  the  Feed  Water  for 
the  Steaming  Boilers: — If  30  pounds  of  feed  water  are  fed 
to  the  boiler  per  horse-power  hour,  and  if  K  —  7,  E  •=.  A, 
tb  =  550,  ts  •=.  350,  tf  =  250,  and  tw  =  90  (about  the  lowest 
temperature  at  which  water  should  enter  the  economizer), 
then  the  square  feet  of  surface  per  horse-power  is 

30  X  (250  —  90) 
Jf?«  =  =  6.1  sq.  ft. 

(550  +  350           250  -f  90     \ 
I 
2                             2  / 

192.  Total  Capacity  of  the  Boiler  Plant  and  the  Number 
of  Boilers  Installed: — The  following  discussion  on  the  size 
of  the  boiler  plant  is  purely  for  illustrative  purposes  and 
is  intended  to  show  how  such  problems  may  be  analyzed. 
In  most  cases  the  exhaust  steam,  and  the  economizer,  if  used, 
will  fall  far  short  of  supplying  the  total  radiation  in  the 
district,  especially  when  the  electrical  output  is  light  and 
the  weather  is  cold.  Suppose  it  be  desired  to  install  extra 
boilers  to  be  used  as  heaters  for  the  radiation  not  supplied 


324  HEATING  AND  VENTILATION 

from  these  two  sources.  To  determine  the  amount  of  extra 
boilers,  find  the  amount  of  radiation  to  be  supplied  by  the 
exhaust  steam  and  the  economizer  and  subtract  this  from 
the  total  radiation.  The  difference  must  be  supplied  by  boil- 
ers used  as  heaters.  It  is  probably  not  safe  to  estimate  too 
closely  on  the  amount  of  exhaust  steam  given  to  the  heating- 
system.  The  maximum  amount  of  44500  pounds  per  hour 
was  obtained,  in  this  case,  by  pumping  one  gallon  of  water 
per  hour  for  each  square  foot  of  radiation  and  by  pumping 
city  water,  in  addition  to  that  obtained  from  the  engines. 
In  heating,  a  less  amount  of  water  than  this  may  be  circu- 
lated even  on  the  coldest  day.  This  is  possible,  first,  be- 
cause water  may  be  carried  at  a  higher  temperature  than 
that  stated,  and  second,  because  there  may  be  less  loss  of 
heat  in  the  conduit,  thus  giving  more  heat  per  gallon  of 
water  to  the  radiation.  Again,  in  estimating  for  a  city 
water  supply,  the  demands  are  not  very  constant  and  are 
difficult  to  estimate.  In  this  one  design  it  was  thought  that 
44500  pounds  per  hour  was  a  very  liberal  allowance  and 
could  be  dropped  to  35000  pounds  (140000  square  feet  of  radi- 
ation), when  estimating  the  amount  of  radiation  supplied 
by  the  exhaust  steam. 

By  Fig.  164  it  will  be  seen  that  the  minimum  load  on  the 
steaming  boilers  carries  through  six  hours  out  of  the  entire 
twenty-four  and  that  the  exhaust  steam  at  this  time  drops 
to  22890  pounds  per  hour,  supplying  91560  square  feet  of 
radiation.  This  minimum  load  is  51  per  cent,  of  the  max- 
imum, and  66  per  cent,  of  the  amount  taken  as  an  average, 
i.  e.,  35000.  The  work  done  by  the  economizer  is  fairly  con- 
stant, since  the  amount  of  economizer  surface  lost  by  the 
steaming  boilers  under  minimum  load  would  be  made  up 
by  the  additional  heating  boilers  thrown  into  service.  On 
the  basis  of  35000  pounds  per  hour,  the  exhaust  steam  and  the 
stack  gases  together  would  heat  170960  square  feet  and 
there  would  be  left  13540  square  feet  (184500  —  20  X  1548  — 
4  X  35000),  to  be  heated  by  additional  boilers.  Under  min- 
imum load  this  would  be  approximately  122500,  leaving  62000 
square  feet  to  be  heated  by  additional  boilers.  If  one  boiler 
horse-power  supplies  160  square  feet  of  radiation,  it  would 
require  84  and  387  boiler  horse-power  respectively  to  supply 
the  deficiency  and  the  total  horse-power  needed  in  each  case 
would  be  1632  and  1935.  A  more  satisfactory  analysis,  how- 


DISTRICT   HEATING  325 

ever,  is  the  following"  which  is  worked  on  the  basis  of  44500 
pounds  per  hour. 

Let  Ws  —  total  number  of  pounds  of  steam  used  in  the 
plant  per  hour  —  approximate  number  of  pounds  of  exhaust 
steam  available  for  heating  the  circulating  water  per  hour; 
Wo  —  equivalent  number  of  pounds  of  steam  evaporated  from 
and  at  212°  ;  \  =  total  heat,  above  32°,  in  one  pound  of  dry 
steam  at  the  boiler  pressure;  q'  =  total  heat,  above  32°,  in 
one  pound  of  feed  water  entering  the  boiler;  then,  if  the 
latent  heat  of  steam  at  atmospheric  pressure  =  970.4  B.  t.  u. 
we  have 

Ws  (X  — ff') 

We    =    -  (123) 

970.4 

and  the  corresponding  boiler  horse-power  needed  as  steam- 
ing boilers  will  be 

We 

Bs.  H.  P.  —  (124) 

34.5 

Next  the  radiation  in  the  district  that  can  be  supplied 
by  the  exhaust  steam  is  Rw  —  4  Ws,  and  the  amount  sup- 
plied by  the  economizer  is  Re  =  20  X  B.  H.  P.  From  which 
we  may  obtain  the  capacity  of  the  heating  boilers,  as 

Total  Radiation  —  4  Ws  —  20  B.  H.  P. 

Bw.  H.  P.  =  (125) 

160 

The  total  boiler  horse-power  of  the  plant  is,  therefore,  the 
sum  of  Bs.  H.  P.  and  Bw.  H.  P.  To  obtain  Equation  125  for  any 
specific  case  one  must  consider  the  maximum  and  minimum 
conditions  of  the  steaming  boiler  plant.  Let  Ws  (max)  = 
maximum  exhaust  steam,  and  Ws  (min)  =  minimum  exhaust 
steam.  Then  for  the  two  following  conditions  we  have, 
Case  1,  where  the  steaming  and  heating  boilers  are  independent  of 
each  other,  the  total  boiler  horse-power  installed  —  Bs.  H.  P.  + 
[total  radiation  —  4  Ws  (min)  —  20  X  B.  H.  P.  in  use]  +  160. 
Also,  Case  2,  where  a  part  or  all  of  the  steaming  boilers  are  piped 
for  both  steaming  and  water  service,  the  total  boiler  horse- 
power installed  =  Bs.  H.  P.  +  [total  radiation  — •  4  Ws  (max)  — 
20  X  B.  H.  P.  in  use]  -h  160.  It  will  be  noticed  that  the  last 
term  representing  the  economizer  service  is  simply  stated 
as  boiler  horse-power  and  no  distinction  is  made  between 
steaming  or  heating  service.  This  term  is  difficult  to  esti- 
mate to  an  exact  figure  because  it  should  be  the  total  horse- 
power in  use  at  any  one  time,  both  steaming  and  heating, 


326  HEATING  AND  VENTILATION 

and  this  can  only  be  obtained  by  approximation.  It  makes 
no  difference  what  service  the  boiler  may  be  used  for,  the 
work  of  the  economizer  is  practically  the  same.  Probably 
the  most  satisfactory  way  is  to  substitute  the  value  of 
Bs.  H.  P.  for  B.  II.  P.  in  the  economizer  and  get  the  approx> 
imate  total  horse-power,  then  if  this  approximate  total 
horse-power  differs  very  much  from  that  actually  needed, 
other  trials  may  be  made  and  new  values  for  the  total  horse- 
power obtained  until  the  equation  is  satisfied. 

APPLICATION. — Let   W*    =    pounds   of   exhaust   steam,   X    = 
1192    (125   pounds   gage   pressure),   and  q'    =    28    (feed   water 
at  60°);  then  when  TT«   =   44500 
We   =   53400 
It*.  H.  P.  =   1548 

184500  —  4X22890  —  20X1548 

Bw.  H.  P.   Case   1    = —    387 

160 

184500  —  4  X  44500  —  20  X  1548 

Bw.  H.  P.  Case  2  =  =   — 153 

160 

This  shows  that  there  is  in  excess  of  waste  heat  in  Case  2, 
making-  a  total  boiler  horse-power,  Case  1,  =  1935  and  Case 
2,  —  1548.  Investigating  Case  1  to  see  what  error  was  intro- 
duced by  using  1548  in  the  economizer,  we  find  approximately 
800  horse-power  of  steam  boilers  in  use,  and  the  total  horse- 
power to  be  1187,  which  is  about  360  horse-power  on  the 
unsafe  side.  Substitute  again  and  check  results.  Case  2  is 
reasonably  close.  In  any  case  the  most  economical  size  of 
boiler  plant  to  install  in  a  plant  requiring  both  steaming  and 
heating  boilers  is  one  where  at  least  a  part,  if  not  all,  of  the 
boilers  are  piped  so  as  to  be  easily  changed  from  one  system 
to  the  other.  By  such  an  arrangement  the  capacity  may  be 
made  the  smallest  possible.  After  obtaining  the  theoretical 
size  of  the  plant,  it  would  be  well  to  allow  a  small  margin 
in  excess  so  that  one  or  two  boilers  may  be  thrown  out  of 
commission  for  repairs  and  cleaning  without  interfering 
with  the  working  of  the  plant.  Case  2  seems  to  be  the  better 
arrangement.  Assuming  1800  total  boiler  horse-power  we 
might  very  well  put  in  six  300  H.  P.  boilers  arranged  in  three 
batteries. 

193.  Cost  of  Heating  from  a  Central  Station  (Direct 
Firing): — It  will  be  of  interest  in  this  connection  to  estimate 
approximately  the  fuel  cost  in  supplying  heat  by  direct  firing 


DISTRICT   HEATING 


327 


to  one  square  foot  of  hot  water  radiation  per  year  from  the 
average  central  station.  In  doing-  this  make  the  boiler  as- 
sumptions the  same  as  Art.  188.-  Take  coal  at  13000  B.  t.  u. 


POWER  PLANT  LAYOUT. 

Fig.   169. 

per  pound,  2000  pounds  per  ton,  and  a  boiler  efficiency  of  60 
per  cent.     Water  enters  the  boiler  at   155   degrees  from   the 


328  HEATING  AND   VENTILATION 

returns,  and  is  delivered  to  the  mains  at  180  degrees.  From 
the  value  of  the  coal  we  have  15600000  B.  t.  u.  per  ton  given 
off  to  the  water.  This  is  equivalent  to  heating-  624000 
p6unds,  or  74910  gallons,  of  water.  If  one  ton  of  coal  costs 
3.50  at  the  plant,  we  have 

350   •*•   74910   =   .0047  cent 

This  represents  the  expense  for  fuel  to  reheat  one  gallon  of 
water,  or  to  supply  one  square  foot  of  heating  surface  one 
hour  at  an  outside  temperature  of  zero  degrees.  Let  the 
average  outside  temperature  for  the  eight  heating-  months 
be  39°  (see  Art.  63).  This  gives  an  average  difference  be- 
tween the  inside  and  outside  temperatures  in  any  residence 
of  70  —  39  =  31  degrees,  and  the  equation  for  the  heat  loss, 
Art.  39,  reduces  to  31  -r-  70  =  .44  of  its  former  value.  Now, 
if.  it  takes  one  gallon  of  water  per  square  foot  of  radiation 
per  hour  under  maximum  conditions,  we  have  for  the  eight 
months  .44  X  8  X  30  X  24  =  2535  gallons  of  water  heated 
for  each  square  foot  of  radiation,  at  a  fuel  expense  of  2535  X 
.0047  =  11.9  cents  per  square  foot  of  radiation  for  the  heat- 
ing year. 

When  the  plant  is  working  under  the  best  conditions 
this  figure  can  be  reduced.  It  can  be  done  with  boilers  of 
a  higher  efficiency  than  that  stated,  or  by  using  a  cheaper 
coal,  both  of  which  are  possible  in  many  cases. 

194.  Cost  of  Heating  from  a  Central  Station.  Summary 
of  Tests: — The  following  tests  we_re  conducted  upon  the 
Merchants  Heating  and  Lighting  Plant,  LaFayette,  Ind.;  one 
in  1906  and  the  other  in  1908.  The  plant  was  changed  slight- 
ly between  the  two  tests  and  the  radiation  carried  upon  the 
lines  was  much  increased,  although  in  all  essential  features 
the  plant  was  the  same.  The  circulating  water  was  heated 
by  exhaust  steam  heaters  and  by  heating  boilers. 

The  plant  had  the  following  important  pieces  of  appara- 
tus employed  in  generating  or  absorbing  the  heat  supply: 

BOILERS    (Steaming  and  Heating). 

Two  125  H.  P.  Stirling  boilers.  Total  heating  surface 
2524  sq.  ft. 

Three  250  //.  P.  Stirling  boilers.  Total  heating  surface 
7572  sq.  ft. 

Pressure  on  steam  boilers  (gage),  150  Ibs. 

Pressure  on  heating  boilers   (approx.),  60  Ibs. 


DISTRICT   HEATING  329 

ENGINES 

One  450  H.  P.  Hamilton  Corliss  comp.  engine,  direct  con- 
nected to  a  300  K.  W.  Western  Electric  72-pole  alternating 
current  generator  120  R.  P.  M.  This  engine  carried  the  load 
of  the  plant  when  it  was  above  50  K.  W.,  which  was  generally 
from  5:30  A.  M.  to  11:30  P.  M.  When  this  unit  was  run, 
direct  current  was  obtained  by  passing  the  alternating  cur- 
rent through  a  motor  generator  set. 

One  125  H.  P.  Westinghouse  comp.  engine,  belted  to  one 
75  K.  W.  3-phase  alternating  and  two  direct  current  genera- 
tors, and  run  at  312  R.  P.  M.  This  unit  was  generally  run 
between  11:30  P.  M.  and  5:30  A.  M. 

One  250  H.  P.  Westinghouse  comp.  engine,  belt  connected 
to  a  200  K.  W.  generator  and  two  smaller  machines. 

PUMPS. 

One  centrifugal,  two-stage  pump,  Dayton  Hydraulic  Co., 
direct  connected  to  a  Bates  vertical  high  speed  engine  at  300 
R.  P.  M. 

Two  Smith-Vaile  horizontal  recip.  duplex  pumps  14  in.  X 
12  in.  X  18  in.  Each  of  the  three  pumps  connected  to  the 
return  main  in  such  a  way  as  to  be  able  to  use  any  combina- 
tion at  any  one  time  to  circulate  the  water.  The  centrifugal 
pump  had  been  in  service  only  one  season.  It  had  a  capacity 
about  equal  to  the  two  reciprocating  pumps  and  under  the 
heaviest  service  this  pump  and  one  of  the  duplex  pumps 
were  run  in  parallel. 

One  Smith-Vaile  horizontal  reciprocating  tank  pump 
6  in.  X  4  in.  X  6  in.  to  lift  the  water  of  condensation  from 
the  exhaust  heater  to  the  tank. 

One  Smith-Vaile  horizontal  reciprocating  make-up  pump 
6  in.  x  4  in.  X  6  in.  to  replace  the  water  that  was  lost  from 
the  system. 

Two  National  horizontal  reciprocating  boiler  feed  pumps. 

One  91/&  in.  Westinghouse  air  pump,  to  keep  up  the  sup- 
ply of  air  through  the  conduits  to  the  regulator  system  in 
the  heated  buildings. 

One  Deane  vertical  deep  well  pump,  to  deliver  fresh 
water  to  the  supply  tank. 

One    Baragwanath    exhaust    steam    heater    or    condenser, 
having  1000  sq.  ft.  of  heating  surface. 


330 


HEATING  AND  VENTILATION 


PARTIAL  SUMMARY  OF  RESULTS. 


1906 

1908 

1. 

Square  feet  of  radiation  

118000 

150000 

2. 

Temperature  of  circulating  water  in 

degrees  F.,  flow  main  

158.36 

164.4 

3. 

Temperature  of  circulating  water  in 

degrees  F.,  return  main  

,       139.9 

139.6 

4. 

Temperature  of  circulating  water  in 

degrees  F.,  after  leaving  heater  

145.6 

147. 

5. 

Temperature    of    outside    air    in    de- 

grees F  

32.6 

37.5 

6. 

Temperature    of    stack    gases    in    de- 

grees F.,  steaming  boiler  

566.8 

7. 

Temperature    of   stack    gases    in    de- 

grees F.,  heating  boiler  

562. 

656. 

8. 

Draft  in  stacks  (all  boilers  average) 

in  inches  of  water  

.689 

.598 

9. 

Heating    value    of    coal    in    B.    t.    u. 

per   pound   

12800 

11565 

10. 

B.   t.   u.  delivered  to  steaming  boiler 

per  hour  by  coal  

.18187000 

25833000 

11. 

B.   t.   u.   delivered   to   heating  boilers 

per  hour  by  coal  

19226000 

27917000 

12. 

B.  t.  u.  delivered  to  circulating  water 

by  heating  boilers  per  hour  

.11800000 

15405000 

13. 

B.  t.  u.  to  be  charged  to  heating  boil- 

ers (Item  12—  Item  15)  

,   7650000 

6934000 

14. 

B.  t.  u.  delivered  to  circulating  water 

by    exhaust    steam    from    the    gener- 

ating engines  per  hour  

,    3600000 

6602000 

15. 

B.    t.    u.    thrown    away    during    test 

from    pump    exhausts    and    available 

for  heating  circulating  water  

4150000 

8471000 

16. 

B.   t.   u.   available   for  heating  circu- 

lating water  from  all  exhaust  steam 

as    in    normal    running    (Item    14     -f- 

Item  15)   

7750000 

15073000 

17. 

Total    B.    t.    u.    given    to    circulating 

water  per  hour  (Item  13   +  Item  16). 

.15400000 

22007000 

18. 

Gallons    of    water    pumped    per   hour 

[Item  17  4-    (8.33   X   Items  2  —  3)]  

.      100000 

108000 

DISTRICT   HEATING  331 

19.  Gallons  of  water  pumped  per  square 
foot    of    radiation    per    hour     (Item 

18    -r-   Item   1)    85  .70 

20.  Efficiency    of    heating-    boilers    (Item 

12   -4-  Item  11)  approx .60  .55 

21.  Value  of  the  coal  in  cents  per  ton  of 

2000  pounds  at  the  plant 200.  175. 

22.  Average   electrical   horse-power 68  141 

Note. — The  above  values  are  averages  and  were  taken 
for  each  entire  test.  The  B.  t.  u.  values  were  considered 
satisfactory  when  approximated  to  the  nearest  thousand. 

195.  Regulation: — The  regulation  of  the  heat  within  the 
residences  is  best  controlled  from  the  power  plant.  In  most 
heating  plants  a  schedule  is  posted  at  the  power  house  which 
tells  the  engineer  the  necessary  temperature  of  the  circu- 
lating water  to  keep  the  interior  of  the  residences  at  70 
degrees  with  any  given  outside  temperature.  The  Merchants 
Heating  and  Lighting  Company  mentioned  above  use  the 
following  schedule: 


Atmosphere 

Water 

Atmosphere 

Water 

60  deg. 

120  deg. 

10  deg. 

190  deg. 

50      " 

140     " 

0     " 

200      " 

40      " 

150      " 

—10     " 

210      " 

30      " 

160      " 

—20      " 

220      " 

20      " 

180      " 

In  addition,  read  the  article  by  Mr.  G.  E.  Chapman,  pub- 
lished in  the  Heating  and  Ventilating  Magazine,  August, 
1912,  page  23,  in  which  he  describes  the  methods  used  in 
regulating  the  Oak  Park,  111.,  plant. 

In  some  heating  plants  the  regulation  is  by  means  of  air 
carried  from  the  compressor  at  the  power  house  through  a 
main  running  parallel  with  the  water  mains  in  the  conduits, 
and  branching-  to  each  building-  where  it  is  used  under  a 
pressure  of  15  pounds  to  operate  thermostats,  which  in  turn 
control  the  water  inlets  to  the  radiators.  A  closer  regula- 
tion is  obtained  in  the  latter  system  than  in  the  former,  but 
it  is  needless  to  say  that  the  thermostats  require  careful 
adjustments  and  frequent  inspections  and  repairs. 

Diaphragms  or  chokes  having-  different  sized  orifices  may 
be  placed  on  the  return  main  from  each  building  to  regulate 
the  supply.  Those  buildings  nearest  to  the  power  plant 


332  TTHATfX*!    AND   VENTILATION 

have  the  advantage  of  a  greater  differential  pressure  than 
those  farther  away,  hence  should  have  smaller  diaphragms. 
By  increasing  the  resistance  in  the  return  line  from  any 
building  the  water  circulates  more  slowly  and  has  time  to 
give  off  more  heat. to  the  rooms.  With  a  high  temperature 
of  the  water  and  a  careful  adjustment  of  the  diaphragms 
it  is  possible  to  have  the  amount  of  water  circulated  per 
square  foot  of  radiation  reduced  much  below  one  gallon  per 
square  foot  per  hour. 

STEAM   SYSTEMS. 

196.  Heating  by  steam  from  a  central  station,  compared 
with  hot  water  heating,  is  a  very  simple  process.  The  power 
plant  equipment  is  composed  of  a  few  inexpensive  parts,  the 
operation  of  which  is  very  simple  and  easily  explained. 
These  parts  have  but  few  points  that  require  rational  de- 
sign. Because  of  the  simplicity  and  the  similarity  to  the 
preceding  discussion  on  hot  water  systems,  the  work  on 
steam  systems  will  be  very  brief.  All  questions  referring 
to  the  construction  of  the  conduit,  the  supporting  of  the 
pipes,  the  provision  for  contraction  and  expansion,  and  the 
draining  of  the  pipes  and  conduits,  are  common  to  both  hot 
water  and  steam  systems  and  are  discussed  in  Arts.  160  and 
161.  A  large  part  of  the  work  referring  directly  to  district 
hot  water  heating  applies  with  almost  equal  force  to  steam 
heating.  This  part  of  the  work,  therefore,  will  deal  with 
such  parts  of  the  power  plant  equipment  as  differ  from 
those  of  the  hot  water  system. 

Centralized  steam  heating  may  be  classified  under  two 
general  heads,  high  pressure  and  low  pressure,  referring  to 
the  pressures  carried  in  the  transmission  lines.  Ordinarily 
steam  is  generated  at  high  pressure  at  the  boiler,  60  to  150 
pounds  gage,  and  reduced  for  line  service  to  pressures  vary- 
ing from  5  to  30  pounds  gage,  with  a  still  further  reduction 
at  the  building  to  pressures  varying  from  0  to  10  pounds 
gage  for  use  in  radiators  and  coils.  Where  exhaust  steam  is 
used  in  the  main,  the  pressure  is  not  permitted  to  go  higher 
than  10  pounds  gage,  because  of  the  back  pressure  on  the 
engine  or  turbine.  Where  exhaust  steam  is  not  used,  the 
pressures  may  be  carried  as  high  as  desired,  thus  allowing 
for'  a  greater  pressure  drop  in  the  line  and  a  corresponding 
reduction  in  pipe  sizes.  (See  Central  Station  Heating  in  De- 


DISTRICT  HEATING 


333 


troit.  Power,  May  7,  1918).  In  large  plants  the  necessity 
for  high  pressures  and  small  pipes  is  apparent.  Even  in 
lines  carrying  exhaust  steam,  high  pressure  feeders  or 
boosters  are  frequently  run  parallel  to  the  heating  main  and 
at  stated  points  connect  to  the  heating  main  through  pres- 
sure reducing  valves.  Vacuum  returns  may  be  applied  to  cen- 
tral station  work  the  same  as  to  isolated  plants.  (See  Art. 
159 — Returning  the  water  to  the  power  plant.  Also,  Chap. 
IX). 

The  principles  involved  in  the  power  plant  end  of  a 
steam  heating  system  may  be  represented  by  Fig.  170.  It 
will  be  seen  that  the  exhaust  steam  from  the  engines  or  tur- 
bines has  four  possible  outlets.  Passing  through  the  oil 
separator,  which  removes  a  large  part  of  the  entrained  oil, 
part  of  the  exhaust  steam  is  turned  into  the  heater  for  use  in 
heating  the  boiler  feed  water.  The  rest  of  the  steam  passes 
on  into  the  heating  system.  If  there  is  more  exhaust  steam 
than  is  necessary  to  supply  the  heating  system,  the  balance 
may  go  to  the  atmosphere  through  the  back  pressure  valve. 
When  the  heating  system  is  not  in  use,  as  would  be  the  case 
in  the  four  warm  months  of  the  year,  the  exhaust  steam 
may  be  passed  into  the  condenser. 


BYPASS  AROUND  HEATER 

TO  BACKPRESSURE  VALVE 


TO HEATER  AND 
BACK  PRESS  VAL 


TO  CONDENSER 


LIVE  3TEAM 
FROM  BOILERS 


Fig.  170. 


It  is  very  -evident,  from  what  has  been  said  before,  that 
it  would  not  be  economical  to  condense  the  steam  in  a  con- 
denser as  long  as  there  is  a  possibility  of  using  it  in  the 
heating  system.  The  increased  gain  in  efficiency,  when  con- 
densing the  exhaust  steam  under  vacuum,  is  very  small  com- 
pared to  the  gain  when  this  same  steam  is  used  for  heating 


334  HEATING  AND  VENTILATION' 

purposes.  It  would  be  also  very  poor  economy  to  use  any 
live  steam  for  heating-  when  there  is  any  exhaust  steam 
wasted.  When  the  amount  of  exhaust  steam  is  insufficient, 
live  steam  is  admitted  through  a  pressure  reducing  valve. 
197.  Drop  in  Pressure  and  the  Diameter  of  the  Mains: — 
The  flow  of  steam  in  a  pipe  follows  the  same  general  law  as 
the  flow  of  water.  The  loss  of  head  may  be  represented 
by  the  well  known  equation, 

2  0  I  r2 

hf  =  (126) 

gd 

where  hf  =  loss  of  head  in  feet,  0  =  coefficient  of  friction, 
v  rr  velocity  in  feet  per  second,  I  =  length  of  pipe  in  feet, 
d  =  diameter  of  the  pipe  in  feet  and  y  =  32.2.  Substitute, 
hf  =  144  p  H-  D,  where  p  =.  drop  in  pressure  in  pounds  and 
D  =  density  of  the  steam,  and  find 

2  0  I  v2  D 

p  =  (127) 

1440  d 

The  coefficient  of  friction  is  found  to  vary  with  the  velocity 
of  the  steam  and  with  the  diameter  of  the  pipe.  Prof.  Unwin 
found  that  for  velocities  of  100  feet  per  second  (good  prac- 
tice for  transmission  lines),  it  could  be  expressed  as  follows, 
where  c  is  a  constant  to  be  found  by  experiment, 


which  when  substituted  in  Equation  127,  gives 
lv2Dc 


72gd 


(128) 


Let  W  —  pounds  of  steam  passing  per  minute  and  (?i  =  diam- 
eter of  pipe  in  inches,  then 


1  /  3.6     \   TT2  Ic 

—     11+ 1- 

.663      I  (/!        I   d^D 


P  =  §    1  + I (129> 

20.663 


The  recommended  value  of  the  constant  c  for  steam  is  .0027. 
Prom  this  equation  we  may  obtain  any  one  of  the  five  terms, 
di,  ~W,  p,  I  or  D,  if  the  other  four  are  known  or  assumed.  In 
the  greatest  number  of  practical  problems  the  item  desired 
is  the  diameter,  dit  and  conditions  must  give  the  pounds  of 
steam  to  be  conveyed  per  minute,  the  pressure  drop  allow- 
able for  its  transmission,  the  length  of  transmission  pipe  and 


DISTRICT   HEATING  335 

the  steam  pressure  (or  density).  In  a  comparatively  few 
problems  W  or  p  may  be  required  and  the  other  four  items 
given. 

APPLICATIONS  BY   THE  USE  OF   EQUATION   129. 

APPLICATION  1. — A  steam  power  main  is  to  be  designed  to 
deliver  8400  pounds  of  steam  per  hour,  at  100  Ibs.  gage  pres- 
sure, through  a  distance  of  1000  feet  of  straight  pipe.  What 
will  be  the  diameter  if  the  allowable  pressure  drop  for  this 
1000  foot  run  is  first,  1  lb.;  second,  %  lb.;  third,  10  Ibs.? 

SOLUTION. — 8400  pounds  per  hour  =  140  pounds  per  min- 
ute. At  100  Ibs.  gage  pressure  the  density  of  the  steam  is 

140  X  140  X  1000  X  .0027 


.258  and  p  = 


/  3.6     \ 

20.663    I  </i      I 


X  .258 


9938           35768 
Reducing  p  — 1 in  which, 

(/!5  «?!« 

when  p   —    1,  (/!  =  6.9"  (area  37.40);  7"  main  required. 
"       p   =    i/2,  di  —  7.8"  (area  47.78);  8"  main  required. 
p   =    10,  di  =  4.5"  (area  15.90);  4%"  main  required. 

APPLICATION  2. — A  4-inch  steam  heating  main  700  feet 
long  is  receiving  steam  at  15  Ibs.  gage  pressure  and  deliver- 
ing it  at  a  pressure  1%  lower.  What  quantity  of  steam  is 
being  delivered?  What  .quantity  will  be  delivered  if  a  drop 
of  three  pounds  is  allowed? 

W-  X  700  X  .0027 


SOLUTION. — .15    — 


(.1742       \ 
.0484    +    1 


1024  X  .072 


.0919  W*  X  700  X  .0027 

~-  = 


n 


=    7.9   lb,   per 

min.  Since  with  everything  else  constant  the  quantity  of 
steam  varies  as  the  square  root  of  the  pressure  drop,  for 
three  pounds  drop  7.9  :  V.T^  as  T^  :  VlT,  whence  Wi  =  4.5  X 
7.9  =  35.6  Ibs.  per  min. 

APPLICATION  3.  —  The  equivalent  length  of  a  4-inch  high 
pressure  steam  main  is  to  be  1600  feet  and  it  will  be  ex- 
pected to  deliver  9000  pounds  of  steam  per  hour  when  the 
pressure  is  150  Ibs.  gage.  What  pressure  drop  will  be  ex- 
perienced when  delivering  this  amount? 


336  HEATING  AND  VENTILATION 

SOLUTION. — 9000  pounds  per  hour  =   150  pounds  per  min- 
ute.    At   150   Ibs.   gage   pressure   the   steam   density  is   .3635, 

(.1742  \      150  X  150  X  1600  X  .0027 
.0484     +    1 
4        I                  1024  X  .3635 

23.8  Ibs. 

APPLICATIONS  BY  TABLE. 


To  avoid  the  time  and  labor  required  in  solving  Equa- 
tion 129,  tables  have  been  compiled  and  curves  plotted.  None 
of  these  time  saving  efforts,  however,  have  produced  a  work- 
ing1 scheme  which  is  perfectly  general,  as  all  have  at  least 
two  of  the  five  variables  constant.  Thus,  Table  39,  Appendix, 
was  compiled  from  Equation  129,  upon  the  basis  of  a  con- 
stant pressure  drop,  p  rr  1  pound,  and  a  constant  pressure 
of  100  Ibs.  absolute  in  the  pipe.  When  these  two  conditions  ob- 
tain, values  may  be  read  directly  from  the  table,  but  when  the  pres- 
sure or  the  pressure  drop  differs  from  these,  corrective  calculations 
must  be  applied  to  the  tabular  values. 

As  may  be  observed  from  the  equation,  the  drop  in  pres- 
sure is  proportional  to  the  square  of  the  pounds  of  steam 
flowing  per  minute  (other  items  constant)  and  the  amount 
delivered  at  any  other  pressure  drop  than  that  of  the  table, 
(1  pound)  will  be  found  by  multiplying  the  reading  from  the 
table  by  the  square  root  of  the  desired  pressure  drop  in 
pounds.  Also,  since  the  weight  of  steam  moved  at  the  same 
velocity  under  any  other  absolute  pressure  is  approximately 
proportional  to  the  absolute  pressures  (other  items  constant), 
the  amount  delivered  at  any  other  pressure  will  be  found  by 
multiplying  the  reading  from  the  table  by  the  square  root 
of  the  ratio  of  the  absolute  pressures.  The  use  of  the  table 
will  be  made  clear  by  the  following  checks  of  Applications 
1,  2  and  3  above. 

Check  1.  Since  the  pressure  in  Application  1  is  100  Ibs. 
gage  and  the  table  is  calculated  for  100  Ibs.  absolute,  quan- 
tities of  steam,  before  insertion  into  table,  must  be  multi- 


plied  by  -J Hence  the  check  of  that  part  of  Applica- 

*    115 

tion  1  having  one  pound  drop  is  as  follows: 

140    X  -\    =:    130    Ibs.    corrected    steam.      In    column 

\    1 1  K 


DISTRICT  HEATING  337 

under  1000  feet,  find  by  interpolation  that  130  Ibs.  per  min- 
ute corresponds  to  a  diameter  of  6.9;  therefore  a  7-inch  main 
is  required.  Before  being-  ready  to  refer  the  quantity  of 
steam  to  the  table  for  checking-  that  part  having  .5  Ib.  pres- 
sure drop,  it  is  necessary  to  apply  corrections  for  both  pres- 
sure and  pressure  drop,  thus, 

140   X  \j x   A/ —   185  Ibs.  corrected  steam.     Un- 

™    115  V       .5 

der  1000  feet,  find  by  interpolation,  that  185  Ibs.  per  minute 
corresponds  to  a  diameter  of  7.8   =  8-inch  main. 
Similarly  the  10  Ib.  drop  is  corrected  by 

/  100 / I 

140  X  AJ    >,X  A/ '  =  41-3  lbs-  corrected  steam.     Un- 

*    115  *      10 

der  1000  feet,  find  by  interpolation,  that  41.3  lbs,  per  minute 
corresponds  to  a  41/£  -inch  main. 

Check  2.  In  Table  39,  under  700  feet,  at  4-inch  diameter, 
the  capacity  of  the  main  is  given  as  36.7  lbs.  for  the  conditions 
of  100  lbs.  pressure  absolute  and  1-lb.  drop  in  pressure.  The 

corrective    factor    for   pressures    is    evidently  -*  / Like- 

*    100 ' 


wise  the  corrective  factor  for  pressure  drop  is-*'  J .     From 

\       1 


V30             /    15 
.    x  A/ •   — 
100           V     1 

7.8  lbs.   per  min.     For  the  3-lb.  drop,  the  corrective  calcula- 

/     30 |~3 
tions  are  36.7   X  A  x  \    —  =  35.5  lbs  per  min. 

^100          *,    1 

Check  3.  In  Table  39,  under  1600  feet,  at  4-inch  diam- 
eter the  capacity  of  the  main  is  given  as  24.4  lbs.  for  condi- 
tions of  100  lbs.  pressure  absolute  and  1-lb.  drop  in  pressure. 
The  corrective  factor  for  pressures  increases  this  as  follows: 


24.4   x  -J —   31.3  ibs.  per  minute,  being-  the  capacity 

v     100 

of  the  main  at  the  problem  pressure,  but  at  the  pressure  drop  of 
the  table,  1-lb.  Since  capacities  are  proportional  to  the  square 
root  of  the  pressure  drops, 

31.3  :  150  as  Vl~:  Vp~whence  p  —   23  pounds  drop. 


338  HEATING  AND  VENTILATION 

It  will  be  seen  that  the  corrections,  necessary  because 
of  the  two  items  assumed  constant,  are  always  made  to 
affect  the  quantity  of  steam  involved,  and  upon  analysis  the  fol- 
lowing general  directions  for  finding  either  a  required  W,  as  in 
Application  2,  or  a  tabular  W,  as  in  Application  1,  will  be 
found  to  hold. 


drop  in  table 


/     pressure  of  table 

Required  W  X  -J  — x    A/ 

*    pressure  required  *     drop  required 

Tabular  W 
Actual  Steam  =  Steam  from  Table  X 


given  pressure  /      given  drop 

X 


\" 


pressure  basis  of  table  drop  in  table 

Steam  to  be  taken  in  Table  =  Actual  Steam  X 


V      pressure  basis  of  table 
-   X   \ 
0*1  xr or*    iiTtkcan  r*o 


drop  in  table 


given  pressure  given  drop 

198.  Dripping:   the    Condensation    from    the   Mains: — The 

condensation  of  the  steam  which  takes  place  in  the  con- 
duit mains,  should  be  dripped  to  the  sewer  or  the  return 
at  certain  specified  points,  through  some  form  of  steam 
trap.  These  traps  should  be  kept  in  first-class  condition. 
They  should  be  inspected  every  seven  to  ten  days.  No  pipe 
should  be  drilled  and  tapped  for  this  water  drip.  The  only 
satisfactory  way  is  to  cut  the  pipe  and  insert  a  tee  with  the 
branch  looking  downward  and  leading  to  the  trap.  The 
sizes  of  the  traps  and  the  distances  between  them  can  only 
be  determined  when  the  pounds  of  condensation  per  running 
foot  of  pipe  can  be  estimated. 

199.  Adaptation  to  Private  Plants: — District  steam  heat- 
ing systems  may  be  adapted  to  private  hot  water  plants  by 
the  use  of  a  "transformer."     This  in  principle  is  a  hot  water 
tube  heater  which  takes  the  place  of  the  hot  water  heater 
of  the  system.     It  may  also  be  adapted  to  warm  air  systems 
by  putting  the  steam  through  indirect  coils  and  taking  the 
air  supply  from  over  the  coils. 

200.  General    Application    of   the    Typical   Design: — The 

following  brief  applications  are  meant  to  be   suggestive  of 


DISTRICT   HEATING  339 

the  method  only,  and  the  discussions   of  the  various  points 
are  omitted. 

Square  feet  of  radiation  in  the  district. — 

Rs  =   184500   X    170   4-  255   =   123000  square  feet. 

Amount  of  heat  needed  in  the  district  to  supply  the  radiation  for 
one  hour  in  zero  weather. — 

Total  heat  per  hour  =   123000   X   255   =  31365000  B.  t.  u. 

Amount  of  heat  necessary  at  the  poioer  plant  to  supply  the  radia- 
tion for  one  hour  in  zero  weather. — Assuming-  15  per  cent,  heat 
loss  in  the  conduit  (this  is  slightly  less  than  that  allowed  for 
the  hot  water  two-pipe  system,  20  per  cent.),  we  have 
31365000  ~  .85  =  36900000  B.  t.  u.  per  hour. 

Total  exhaust  steam  available  for  heating  purposes. — 
Ws  (max.)  =   (23100  +  8680)    X   1.15  =  36547  pounds  per  hour. 
W»  (min.)    =   (   1490  +  8680)   X   1.15  =  11696  pounds  per  hour. 

Total  B,  t.  u.  available  from  exhaust  steam  per  hour  for  heating. — 
Let  the  average  pressure  in  the  line  be  5  pounds  gage  and 
let  the  water  of  condensation  leave  the  indirect  coils  in  the 
residences  at  140  degrees.  We  then  have  from  one  pound  of 
exhaust  steam,  by  Equation  97, 

B.  t.  u.  =  .85   X   960  +   196  —  (140  —  32)   =  904 
Assuming  this  to  be  900  B.  t.  u.  per  pound,  the  total  available 
heat  from  the  exhaust  steam  for  use  in  the  heating  system  is, 
maximum  total  rr  32892300  B.  t.  u.  and  the  minimum  total,  = 
10526400  B.  t.  u. 

Square  feet  of  steam  radiation  that  can  be  supplied  by  one  pound 
of  exhaust  steam  at  5  pounds  gage. — 

Rs   -  900   ^-    (255   -T-   .85)    =   3. 

Total  B.  t.  u.  to  be  supplied  by  live  steam. — 

B.  t.  u.  (max.  load)   =  36900000  —  32892300  —     4007700  B.  t.  u. 
B.  t.  u.   (min.    load)   =  36900000  —  10526400  =  26373600  B.  t.  u. 

Total  pounds  of  live  steam  necessary  to  supplement  the  exhaust 
steam. — Let  the  steam  be  generated  in  the  boiler  at  125 
pounds  gage.  With  feed  water  at  60  degrees 

Max.  load  =     4007700  -4-  1164  =     3444  pounds. 
Min.    load  =   26373600   -T-   1164  =   22661  pounds. 

Boiler  horse-pcnver  needed  for  the  steam  power  units. — As  in 
Arts.  189  and  192. 

B,.  H.  P.   (max.)    =   36547    X    1.2    -=-   34.5   =   1271. 
B,.  a.  P.   (min.)     r=   11696    X    1.2   -f-   34.5   =      407. 

Total  boiler  horse-power  needed  in  the  plant. — Maximum  load. 
B.  n.  P.  (total)  =  1271  +  (3444  X  1.2  -f-  34.5)  =  1391. 


340 


HEATING  AND  VENTILATION 


It  will  be  noticed  that  this  total  horse-power  is  157 
horse-power  less  than  the  corresponding  Case  2  in  Art.  192. 
This  is  accounted  for  by  the  fact  that  no  steam  is  used  up  in 
work  in  the  circulating-  pumps,  also  that  the  conditions  of 
steam  generation  and  circulation  are  slightly  different.  1500 
boiler  horse-power  would  probably  be  installed  in  this  case. 

Size  of  conduit  mains. — Let  it  be  required  to  find  the  diam- 
eters of  the  main  system  in  Fig.  166  at  the  important  points 
shown.  Art.  169  gives  the  length  of  the  mains  in  each  part. 
Allow  .3  pound  of  steam  for  each  square  foot  of  steam  radia- 
tion per  hour  (this  will  no  doubt  be  sufficient  to  supply  the 
radiation  and  conduit  losses).  Try  first,  that  part  of  the  line 
between  the  power  plant  and  A,  with  an  average  steam  pres- 
sure in  the  lines  of  about  5  pounds  gage  and  a  drop  in  pres- 
sure of  1%  ounces  per  each  100  feet  of  run  (approximately 
5  pounds  per  mile).  25200  pounds  per  hour  gives  W  —  420. 
The  length  of  this  part  of  the  line  is  200  feet  and  the  drop  is 
3  ounces,  or  .19  pound. 

420  I    100 

W  (table)  =;-      -  X    -J  -  2158  pounds 

V.19  *      20 

which  gives  a  15  inch  pipe. 

Following  out  the  same  reasoning  for  all  parts  of  the 
line,  we  have 

TABLE  XXXIX. 


PP 
to  A 

AtoB 

BtoC 

CtoD 

DtoE 

Distance  between  points  :  

200 

500 

1500 

1500 

500 

Radiation  supplied,  sq.  ft. 

84000 

57000 

34000 

19000 

8000 

Pressure-drop  in  pounds  =  p  

.19 

.47 

1.4 

1.4 

.47 

Diam.  of  pipe  in  inches,  by  table. 

15 

13 

11 

9 

5 

In  general  practice,  these  values  would  probably  be 
taken  16,  14,  12,  10  and  6  inches  respectively.  Look  up 
Table  39,  Appendix,  and  check  the  above  figures. 


CHAPTER  XIV. 


TEMPERATURE    CONTROL,    IN    HEATING    SYSTEMS. 

201.  From   tests   that  have   been   conducted   on   heating 
systems,   it  has  been   shown  that   there  is  less  loss  of  heat 
from    buildings   equipped    with    automatic   temperature    con- 
trol, than  from  buildings  where  there  is  no  such  control.     A 
uniform   temperature  within   the  building   is  desirable   from 
all   points   of   view.     Where   heating   systems   are    operated, 
even   under    the    best    conditions    without    such    control,    the 
efficiency  of  the  system  would  be  increased  by  its  applica- 
tion.    No  definite  statement  can  be  made  for  the  amount  of 
heat  saved,  but  it  is  safe  to  say  that  it  is  between  5  and  20 
per   cent.     A   building    uniformly   heated    during   the    entire 
time,  requires  less  heat  than  if  a  certain  part  or  all  of  the 
building    were    occasionally    allowed    to    cool    off.      When    a 
building  falls  below  normal  temperature  it  requires  an  extra 
amount  of  heat  to  bring  it  up  to  normal,  and  when  the  in- 
side temperature  rises  above  the  normal,  it  is  usually  low- 
ered by  opening  windows   and   doors   to   enable   the  heat  to 
leave  rapidly.     High  inside  temperatures  also  cause  a  corre- 
spondingly  increased   radiation   loss.      Fluctuations   of   tem- 
perature, therefore,  are  not  only  undesirable   for  the   occu- 
pants, but  they  are  very  expensive  as  well. 

202.  Principles    of    the     System: — Temperature    control 
may  be  divided  into  two  general  classifications, — small  plants 
and  large  plants.     The  control  for  small  plants,  i.  e.,  such  plants 
as  contain  very  few  heating  units,  is  accomplished  by  regu- 
lating   the    drafts    by    special    dampers    at    the    combustion 
chamber.     This  method  controls  merely  the  process  of  com- 
bustion and  has  no  especial  connection  with  individual  reg- 
isters or  radiators,   it  being  assumed  that  a  rise   or  fall  of 
temperature    in    one    room    is    followed    by    a    corresponding 
effect  in  all  the  other  rooms.     This  method  assumes  that  all 
the   heating   units   are   very  accurately   proportioned    to   the 
respective    rooms.      The    dampers   are    operated    by   a    motor 
device  which   in   turn   is   driven  by   springs  or   weights   and 
controlled    by    a    thermostat    and    electric    batteries.       This 
system  of  regulation  may  be  applied  to  any  system  of  heat. 


342 


HEATING  AND  VENTILATION 


Thermostat  set  on  wa// 
//?  room  above 


Fig.  171  shows  a  typical  appli- 
cation to  a  small  steam  boiler 
plant.  Furnace  systems  require 
thermostatic  control  only  be- 
tween the  room  and  the  dam- 
pers; closed  hot  water,  steam 
and  vapor  systems,  however, 
should  have  additional  regula- 
tion from  the  pressure  within 
the  boiler  to  the  draft.  Occa- 
sionally in  the  morning  the 
pressure  in  these  systems  may 
become  excessive  before  the 
house  is  heated  enough  for  the 
thermostat  to  act.  With  such 
dual  regulation  no  hot  water 
heater  or  steam  boiler  would  be 
forced  to  a  dangerous  pressure. 
Fig.  172  represents  a  standard 
form  of  the  thermostat  supplied 
Fig.  171.  by  the  Andrews  Heating  Co. 

and  the  Minneapolis  Regulator  Co.     The  complete  regulator 
has  in  addition  to  this,  two  cells  of  open  circuit  battery  and 
a  motor  box   (Fig.  171),  all  of  which  illustrate 
very  well  the  thermostatic  damper  control. 

The  thermostat  operates  by  a  differential 
expansion  of  the  two  different  metals  com- 
posing the  spring  at  the  top.  Any  change  in 
temperature  causes  one  of  the  me.tals  to  ex- 
pand or  contract  more  rapidly  than  the  other 
and  gives  a  vibrating  movement  to  the  project- 
ing arm.  This  is  connected  with  the  batteries 
and  with  the  motor  in  such  a  way  that  when 
the  pointer  closes  the  contact  with  either  one 
of  the  contact  posts,  a  pair  of  magnets  in  the 
motor  causes  a  crank  arm  to  rotate  through 
180  'degrees.  A  flexible  connection  between  this 
crank  and  the  damper  causes  the  damper  to 
V  jj/  open  or  close.  A  change  in  temperature  in 


Fig.  172. 


the  opposite  direction  makes  contact  with  the 
other   post   and   reverses  the  movement   of  the 


TEMPERATURE   CONTROL 


Fig".  173. 


crank  and  damper.  The 
movement  of  the  arm  be- 
tween the  contacts  is  very 
small  thus  making  the 
thermostat  very  sensitive. 
No  work  is  required  of  the 
battery  except  that  neces- 
sary to  release  the  motor. 

Occasionally  it  is  desira- 
ble to  connect  small  heat- 
ing plants  having  only  one 
thermostat  in  control,  to  a 
central  station  system.  Fig. 
173  shows  how  the  supply 
of  heat  may  be  controlled 
by  the  above  method. 

Temperature  control  in  large 
plants,  i.  e.,  those  plants 
having  a  large  number  of 
heating  units,  is  much  more 
complicated.  The  following 
discussion  will  apply  espe- 
cially to  hot  water  and 
steam  systems,  and  will  be 
additional  to  the  control  at 


Fig.  174. 


344 


HEATING  AND  VENTILATION 


the  heater  and  boiler  as  discussed  under  small  plants.  Fig. 
174  shows  a  typical  layout  of  such  a  system.  Compressed 
air  at  15  pounds  gage  is  maintained  in  cylinder,  Su,  which  is 
located  in  some  convenient  place  for  the  attendant.  This  air 
is  carried  to  the  thermostat,  Th,  on  one 
of  the  protected  walls  in  the  room.  Here 
it  passes  through  a  controlling  valve 
and  is  then  led  to  the  regulating-  valve 
on  the  radiator  where  it  acts  on  the  top 
of  a  rubber  diaphragm  as  shown  in  Fig. 
175  to  close  the  valve  and  to  cut  off  the 
supply.  When  the  room  cools  off,  the 
controlling  valve  at  Th  cuts  off  the  sup- 
ply and  opens  the  radiator  air  line  to  the 
atmosphere.  This  removes  the  air  pres- 
sure from  above  the  diaphragm  and  per- 
mits the  stem  of  the  valve  to  lift.  On  the 


Fig.  175. 


opening  of  the  valve  the  steam  or  water  again  enters  the 
radiator  and  the  cycle  is  completed. 

Fig.  139  shows  the  application  of  thermostatic  control 
to  blower  work.  In  this  system  (single  duct  system)  the 
thermostat  B  and  the  mixing  dampers  are  located  at  the  ple- 
num chamber.  The  same  general  arrangement  may  be  ap- 
plied to  the  double  duct  system,  with  the  dampers  in  the 
wall  at  the  base  of  the  vertical  duct  leading  to  the  room. 

203.     Some  of  the  Important  Points  in  the  Installation: — 

Each  radiator  has  its  own  regulating  valve.  All  rooms 
having  three  radiators  or  less  are  provided  with  one  thermo- 
stat. Large  rooms  having  four  or  more  radiators  have  two 
or  more  thermostats  with  not  more  than  three  radiators  to 
the  thermostat.  Where  other  motive  power  is  not  available 
for  the  air  supply,  a  hydraulic  compressor  is  used.  This 
compressor  automatically  maintains  the  air  pressure  at  15 
pounds  gage  in  the  steel  supply  tank.  The  main  air  trunk 
lines  are  galvanized  iron,  %-  and  %-inch  in  diameter,  and 
are  tested  under  a  pressure  of  25  pounds  gage.  All  branch 
pipes  are  ^4-  and  %-inch  galvanized  iron.  Fittings  on  the 
%-inch  pipes  are  usually  brass.  Where  flexible  connections 
are  made,  this  is  sometimes  done  by  armoured  lead  piping. 
Thermostats  are  usually  provided  with  metallic  covers  and 
are  finished  to  correspond  with  the  hardware  of  the  respec- 
tive rooms.  Each  thermostat  is  provided  with  a  thermom- 


TEMPERATURE   CONTROL  345 

eter  and  a  scale  for  making"  adjustments.  Each  radiator  is 
provided  with  a  union  diaphragm  valve  having-  a  specially 
prepared  rubber  diaphragm  with  felt  protection.  This  valve 
replaces  the  ordinary  radiator  valve.  One  of  these  valves  is 
used  on  the  end  of  each  hot  water  radiator,  one  on  each  one- 
pipe  steam  radiator  and  two  on  each  two-pipe  low  pressure 
steam  radiators.  This  last  condition  does  not  hold  for  two- 
pipe  steam  radiators  with  mechanical  vacuum  returns,  in 
which  case  patented  specialties  are  applied  by  the  vacuum 
company.  In  such  cases  the  supply  to  the  radiator  only  is 
controlled.  In  any  first  class  system  of  control,  the  tempera- 
ture of  the  room  may  easily  be  kept  within  a  maximum 
fluctuation  of  three  degrees. 

204.  Some  Special  Designs  of  Apparatus: — All  tempera- 
ture control  work  is  solicited  by  specialty  companies,  each 
having  a  patented  system.  In  the  essential  features  these 
systems  all  agree  with  the  foregoing  general  statements. 
The  chief  difference  is  in  the  principle  upon  which  the  ther- 
mostat, Th,  operates. 

Fig.  176  shows  sections  through  the  intermediate  and 
positive  thermostats  manufactured  by  the  Johnson  Service 
Company,  Milwaukee.  The  interior  workings  of  the  ther- 
mostats are  as  follows:  Intermediate. — Air  enters  at  A  from 
the  supply  tank,  passes  into  chamber  B  and  escapes  at  port 
C.  If  thermostatic  strip  T  expands  inward  to  close  C,  the 
air  pressure  collects  in  B  and  presses  down  port  valve  V, 
thus  opening  port  E,  letting  air  through  into  F  and  out  at  O 
to  close  the  damper.  When  T  expands  outward,  pressure  at 
B  is  relieved  and  V  is  forced  back  by  a  spring,  closing  E. 
Air  in  F  reacts  against  the  diaphragm  and  escapes  through 
hollow  valve  V  at  H,  permitting  the  damper  to  open.  Posi- 
tive.— Air  enters  at  A,  passes  into  chamber  B  and  escapes 
at  C.  If  thermostatic  strip  T  expands  inward  to  close  C,  air 
pressure  collects  in  B,  forces  out  the_  knuckle  joint  K  and 
operates  the  three-way  valve  V,  thus  shutting-  port  E  and 
opening  port  F,  letting  air  escape  and  radiator  valve  open. 
When  T  expands  outward,  pressure  at  B  is  relieved,  knuckle 
joint  K  returns,  pulling  V  outward,  thus  shutting  port  F, 
opening  E,  letting  air  escape  through  G  and  shutting  off 
radiator  valve. 

The  real  thermostat  is  the  spring  T.  This  is  composed 
of  steel  and  brass  strips  brazed  together.  Because  of  a 


346 


HEATING  AND   VENTILATION 


higher  coefficient  of  expansion  in  the  brass  than  in  the 
steel,  a  change  in  the  room  temperature  causes  the  spring- 
to  move  toward  or  away  from  the  seat  ('.  T  is  adjustable 
for  any  desired  room  temperature.  The  intermediate  ther- 
mostat is  used  on  indirect  heating  where  mixing  dampers 
are  employed  and  where  an  intermediate  position  of  the 
valve  is  necessary.  The  positive  thermostat  is  used  on  direct 
radiators  and  coils  where  a  full  open  or  full  closed  move- 
ment of  the  valve  is  desired. 

INTERMEDIATE 


Fig.  176. 


Fig.  177  shows  a  section  through  pattern  K  thermo- 
stat, manufactured  by  the  Powers  Regulator  Co.,  Chicago. 
This  thermostat  consists  of  a  frame  carrying  two  corrugated 
disks,  brazed  together  at  the  circumference  and  containing  a 
volatile  liquid  having  a  boiling  point  at  about  50  degrees  F. 
At  a  temperature  of  about  70  degrees,  the  vapor  within 
the  disks  has  a  pressure  of  about  6  pounds  to  the  square 
inch.  This  pressure  varies  with  every  change  of  tempera- 


TEMPERATURE   CONTROL 


347 


ture  and   produces   variations   in   the   total   thickness   of   the 
center  of  the  disks. 

The  compressed  air  enters  at  H  and  passes  into  chamber 
N  through  the  controlling-  valve  -/,  which  is  normally  held  to 
its  seat  by  a  coil  spring-  .under  cap  P.  Within  the  flange  M 
is  located  an  escape  valve  L  upon  which  the  point  of  the 
supply  valve  J  rests.  Valve  L  tends  to  remain  open  when 
permitted  by  reason  of  the  spring  underneath  the  cap.  When 
the  temperature  rises  sufficiently  to  cause  the  disks  to  in- 
crease in  thickness  and  move  the  flange  M,  the  first  action 
is  to  seat  the  escape  valve  L,  its  spring  being  weaker  than 
that  above  •/.  If  the  expansive  motion  is  continued  after 


Fig.  177. 

valve  L  is  seated,  the  valve  J  is  then  lifted  from  its  seat 
and  compressed  air  flows  into  the  chamber  N.  As  the 
air  accumulates  in  chamber  X,  it  exerts  a  pressure  upon  the 
elastic  diaphragm  K  in  opposition  to  the  expansive  force  of 
the  disk.  So,  whenever  there  is  sufficient  pressure  in  N  to 
balance  the  power  exerted  by  the  disks,  the  valve  J  returns 
to  its  seat  and  no  more  air  is  permitted  to  pass  through. 
If  the  temperature  falls,  the  pressure  within  the  disks  be- 
comes less,  the  disks  draw  together  and  the  over-balancing 


348 


HKATIXd  AND  VENTILATION 


air  pressure  in  X  reverses  the  movement  of  the  flange  M  and 
permits  the  escape  valve  L  under  the  influence  of  its  spring 
to  rise  from  its  seat,  whereupon  a  portion  of  the  air  in  N 
is  discharged  until  the  pressure  in  N  becomes  equal  to  the 
diminished  pressure  from  the  disks.  Thus  the  pressure  of 
the  air  in  N  is  maintained  always  in  direct  proportion  to  the 
expansive  power  (temperature)  of  the  disks.  Port  /  con- 
nects with  chamber  A'  and  leads  to  the  diaphragm  valve. 

This  thermostatic  valve  controls  the  regulator  valve  by 
a  graduated  movement  and  is  used  on  the  dampers  for 
blower  work.  Another  form  with  maximum  movement  only 
is  designed  for  steam  systems. 

Pig.  178  shows  the  positive  and  graduated  thermostats 
as  manufactured  by  the  National  Regulator  company,  Chi- 
cago. The  thermostatic  element  in  these  thermostats  is  the 
vulcanized  rubber  tube  A,  which  changes  its  length  with  the 
varying  room  temperatures  and  causes  the  valve  O  to  open 
or  close  the  port  G,  thus  controlling  the  supply  of  air  to 


POSITIVE 


INTERMEDIATE 


Fig.  178. 

and  from  the  radiator  valve  or  the  regulating  damper.  In 
the  positive  thermostat  air  enters  the  tube  from  the  supply 
through  the  filter  and  restricted  passage  P.  From  the  in- 
terior of  the  tube  the  air  leaves  through  the  middle  orifice 
and  enters  the  pipe  leading  to  the  radiator  valve.  If  the 


TEMPERATURE   CONTROL,  349 

room  temperature  is  above  the  normal,  port  G  closes  and  the 
air  pressure  collects  in  the  tube,  thus  creating-  a  pressure 
in  the  line  leading  to  the  radiator  valve  and  closing  it.  If 
the  room  temperature  falls  below  the  normal,  port  G  opens, 
air  is  exhausted  from  the  tube  to  the  atmosphere,  the  pres- 
sure on  the  radiator  valve  is  released  and  the  valve  opens. 
The  intermediate  thermostat  differs  from  the  positive  ther- 
mostat in  having  but  one  air  line.  Room  temperatures 
below  the  normal  contact  tube  A,  open  port  G,  and  exhaust 
the  air  to  the  atmosphere.  With  this  release  in  pressure  in 
the  pipe  at  P  the  regulating-  damper  is  turned  to  admit 
more  warm  air  into  the  room.  With  the  room  temperature 
above  the  normal,  tube  A  expands,  port  G  closes,  pressure  in 
pipe  P  increases  and  the  regulating  damper  is  turned  so  as 
to  admit  a  lower  temperature  of  air  in  the  room.  By  means 
of  this  a  graduated  movement  of  the  damper  is  obtained. 


CHAPTER  XV. 
ELECTRICAL,  HEATING. 


In  the  present  state  of  the  heating  business  it  seems 
almost  unnecessary  to  discuss  electrical  heating,  in  any 
serious  way,  in  connection  with  steam  power  plants.  The 
reasons  will  be  seen  in  the  following  brief  discussion. 
Electrical  heating  can  appeal  to  the  public  only  from  the 
standpoint  of  convenience,  since  a  comparison  of  economies 
between  steam,  hot  water  or  warm  air  heating  on  one  hand, 
and  electrical  heating  on  the  other,  is  wholly  against  the 
latter.  Its  application  to  the  process  of  heating  will  find 
its  greatest  economy  in  connection  with  water  power  plants 
where  the  combustion  of  fuel  is  eliminated  from  the  prop- 
osition. This  discussion  will  not  bear  in  any  way  upon  the 
water  power  generator. 

205.  Equations  Employed  in  Electrical  Heating  Design  :— 
1  H.  P.  =  746  watts. 

1  H.  P.  =  33000  ft.  Ibs.  per  min.   =  1980000  ft.  Ibs.  per  hr. 

1  B.  t.  u.  =  778  ft.  Ibs. 

1   H.  P.  hr.  =   1980000  -f-  778  =   2545  B.  t.  u.  per  hr. 

1  H.  P.  hr.  =  746  watt  hours  =  2545  B.  t.  u.  per  hr. 

1  watt  hr.  =  3.412  B.  t.  u.  per  hr. 

1  watt  hr.  =  3.412  -j-  170  rr  .02  sq.  ft.  of  hot  water  rad. 

1  watt  hr.  =  3.412  -^  255  =  .0134  sq.  ft.  of  steam  rad. 

1   kilo-watt  hr.  =  20.1  sq.  ft.  of  hot  water  rad.  (130) 

1   kilo-watt  hr.  rr  13.4  sq.  ft.  of  steam  rad.  (131) 

206.  Comparison    between    Electrical    Heating    and    Hot 
"Water  and   steam    Heating: — The  loss   in  transmitting  elec- 
tricity from  the  generators  through  the  switchboard  to  the 
radiators  may  be  small  or  large,  depending  upon  the  condi- 
tions of  wiring,  the  current  transmitted  and  the  pressure  on 
the    line.      In   all   probability   it   would   equal   or   exceed    the 
transmission  losses  in  hot  water  or  steam  lines.     Assuming 
these  losses  to  be  the  same,  a  fair  comparison  may  be  made 
in  the  cost  of  heating  by  the  various  methods.     The  operat- 
ing efficiency  of  an  electric  heater  is  100  per  cent.,  since  all 
the  current   that   is   passed   into   the  heater   is   dissipated   in 


ELECTRICAL   HEATING  351 

the  form  of  heat  and  no  other  losses  are  experienced.  This 
is  not  true  of  steam  systems  where  the  water  of  condensa- 
tion is  thrown  away  at  fairly  high  temperatures.  Where 
electricity  or  steam  is  generated  and  distributed  all  in  the 
same  building,  there  is  no  line  loss  to  be  accounted  for, 
since  all  of  this  heat  goes  to  heating  the  building  and  counts 
as  additional  radiation. 

Equations  130  and  131  show  the  theoretical  relation 
existing  between  electrical  heating  and  hot  water  and  steam 
heating  compared  at  the  power  plant.  The  following  dis- 
cussion is  based,  therefore,  upon  the  assumption  that  1  kilo- 
watt hour,  in  an  electric  radiator,  will  give  off  the  same 
amount  of  heat  as  20.1  and  13.4  square  feet  of  hot  water  and 
steam  radiation  respectively.  With  coal  having  13000  B.  t.  u. 
per  pound  and  a  furnace  efficiency  of  60  per  cent.,  it  will 
require  3412  -f-  7800  =  .44  pound  of  coal  per  hour.  If  coal 
costs  $2.00  per  ton  of  2000  pounds,  there  will  be  an  actual 
fuel  expense  of  .044  cent.  On  the  other  hand,  assuming  the 
combined  mechanical  efficiency  of  an  engine  or  turbo-gener- 
ator set  to  be  90  per  cent.,  the  heat  from  the  steam  that  is 
turned  into  electrical  energy  per  hour  is  1000  -4-  .90  =  1111 
watts,  for  each  kilo-watt  delivered.  Now  if  this  unit  has 
15  per  cent,  thermal  efficiency,  we  have  the  initial  heat  in 
the  steam  equivalent  to  1111  -4-  .15  =r  7400  watt  hours.  From 
this  obtain  7400  X  3.412  =  25249  B.  t.  u.  per  hour;  or,  25249  -f- 
7800  =  3.2  pounds  of  coal  per  hour.  This,  at  the  same  rate 
as  shown  above,  would  be  worth  .32  cent.  Comparing,  the 
electrical  generation  actually  costs  7.2  times  as  much  as  the 
other.  This  comparison  has  dealt  with  the  fuel  costs  at  the 
plant  and  has  not  taken  into  account  the  depreciation,  labor 
costs,  etc.,  the  object  being  to  show  relative  efficiencies  only. 

Another  way  of  looking  at  this  subject  is  as  follows:  a 
fairly  large  turbo-generator  set  (say  500  K.  W.)  will  deliver 
1  kilo-watt  hour  to  the  switchboard  on  20  pounds  of  steam. 
With  10  per  cent,  additional  steam  for  auxiliary  units,  this 
amounts  to  22  pounds  of  steam  per  kilo-watt  hour  at  the 
switchboard.  One  pound  of  steam  generated  in  a  plant  of 
this  kind  with  the  above  efficiencies  and  value  of  coal,  also 
with  a  steam  pressure  of  150  pounds  and  a  good  feed  water 
heater,  will  give  to  each  pound  of  steam  approximately  1000 
B.  t.  u.  This  makes  22000  B.  t.  u.  or  2.8  pounds  of  coal  re- 

v 


352  HEATING  AND  VENTILATION 

quired  to  each  kilo-watt  output.  This  is  about  10  per  cent, 
less  than  the  above  figures. 

The  ratio  of  7  to  1,  as  shown  in  the  above  efficiencies, 
does  not  seem  to  hold  good  in  the  selling  price  to  the  con- 
sumer. In  round  numbers,  district  steam  and  hot  water 
heating  systems  supply  25000  B.  t.  u.  to  the  consumer  for 
one  cent.  The  cost  for  electrical  energy  to  the  consumer  is 
between  6  and  7  cents  per  kilo-watt.  This  gives  3412  -r- 
6.5  =  525  B.  t.  u.  for  one  cent.  Comparing  with  the  above, 
gives  a  ratio  of  48  to  1. 

207.  The  Probable  Future  of  Electrical  Heating: — Be- 
cause of  the  low  efficiency  of  electrical  heating  as  compared 
with  other  methods  of  heating,  it  is  very  probable  that  it  will 
not  replace  the  other  methods  in  sections  of  the  country 
having  severe  or  changeable  climate,  except  in  so  far  as  the 
convenience  of  the  user  is  the  principal  thing  sought  for,  and 
the  expense  of  operating  a  minor  consideration. 

On  the  other  hand,  in  limited  sections  of  the  country 
where  conditions  are  favorable  (sections  of  the  Pacific  Coast 
for  example),  heating  by  electricity  is  rapidly  increasing. 
Hydro-electric  power  at  a  low  rate  and  a  climate  that  re- 
quires only  a  small  amount  of  heat  in  the  buildings,  morn- 
ing and  evening,  make  electric  heating  an  actual  economy. 
In  such  a  climate  the  cumbersome  coal  and  oil  burning  steam 
and  water  heating  systems  would  be  inappropriate,  while 
the  starting  and  the  banking  of  fires  when  not  needed  would 
be  a  wasteful  process* 

While  in  most  cases  electricity  will  be  barred  from  the 
usual  heating  and  laundry  processes,  it  will  continue  to  be 
increasingly  used  in  those  household  economies  where  tem- 
peratures are  needed  above  250°,  such  as  percolators,  grills, 
toasters,  broilers,  plate  warmers,  ranges  and  ovens.  Electric 
ovens  in  bakeries  are  being  employed  because  they  occupy 
much  less  space  than  the  brick  oven  of  same  capacity,  are 
light  in  weight,  are  more  cleanly,  can  be  regulated  more 
easily  and  use  the  heat  generated  much  more  effectively. 


CHAPTER  XVI. 


REFRIGERATION. 


DESCRIPTION   OF    SYSTEMS    AND    APPARATUS. 

208.  General  Di visions  of  the  Subject: — The  rapidly   in- 
creasing demand  for  the  cold  storage   of  food   products,   the 
production  of  artificial  ice  and  the  cooling  of  buildings  have 
developed    for    the    heating    engineer    a    broad    and    inviting 
field,   namely,   refrigeration.      A  municipal   electric   or  pump- 
ing station  with  a  district  heating  plant   to   utilize   the   ex- 
haust  steam   in   winter  and   a   refrigeration   plant   to   utilize 
the    same    in    summer    furnishes    a    unique    opportunity    for 
economic  engineering.     One  application  of  the  above  princi- 
ple where  a  10-ton   ice  plant  of  the  absorption  type  was  so 
operated  in  a  town  of  3500  population  and  earned  a  dividend 
of  13  per  cent,  on  the  investment,  is  proof,  if  any  is  needed, 
that  the  field  is  an  intensely  practical  one. 

As  in  heating  systems  there  must  be  sources  of  heat, 
circulating  mediums,  distributing  systems  and  delivering 
systems  whereby  the  carriers  give  up  their  heat  at  the 
proper  places  in  the  circuits,  so  in  refrigerating  systems 
there  must  be  sources  of  minus  heat  or  of  heat  abstraction, 
circulating  mediums,  distributing  systems  and  receiving  sys- 
tems whereby  the  carriers  take  up  heat  at  the  proper  places 
in  the  circuits  from  articles  or  rooms  that  are  being  cooled. 
The  carriers  (circulating  mediums),  and  the  receiving  and 
transmitting  of  the  heat  to  and  from  them  present  no  special 
difficulties  or  great  diversity  of  practice,  but  in  the  methods 
of  producing  and  maintaining  the  sources  of  minus  heat 
there  are  considerable  differences  and  numerous  methods. 

209.  Refrigerating    Systems    may    be    divided    into    two 
groups,  those  producing  cold  by  more  or  less  chemical  action 
between  ingredients  upon  mixing,  called  chemical  systems,  and 
those  producing  cold  by  the   evaporation   of  a  liquefied   gas 
or  the  expansion  of  a  compressed  gas,  called  mechanical  sys- 
tems.    Chemical  systems  are  used  only  occasionally  in  com- 
mercial work,  but  are  frequently  found  in  small  sized  plants 
for   domestic   purposes.      Low   first    cost   and    convenience   of 


354 


HEATING  AND   VENTILATXOX 


handling  are  the  principal  advantages.  This  division  in- 
cludes the  simple  melting  of  ice  and  the  mixing  of  ice  and 
salt  for  temperatures  as  low  as  0  to  — 5  degrees.  The  latter 
is  much  used  in  domestic  processes  for  the  production  of 
table  ices.  etc.  Other  ingredients  used  in  the  mixtures  with 
the  corresponding  temperature  drops  which  may  be  ex- 
pected are  given  in  Table  58,  Appendix.  The  chemical 
method  of  producing  cold  is  occasionally  used  to  maintain 
low  temperatures  in  storage  rooms  while  repairs  are  being 
made  upon  the  regular  machinery.  The  chemical  methods 
of  cooling  are  so  simple  in  principle  that  they  will  not  be 
discussed  further  in  this  work.  Mechanical  systems  include 
all  the  practical  methods  of  commercial  refrigeration.  These 
are,  the  vacuum  system,  the  cold  air  system,  the  compression  system 
and  the  absorption  system. 


210.  Vacuum  Systems: — This  system  was  formerly  of 
some  importance  but  of  late  years  has  given  place  to  other 
and  more  efficient  methods.  Fig.  179  shows  a  vacuum  sys- 
tem in  diagram.  If  a  spray  of  water 
or  brine  is  injected  into  a  chamber 
that  contains  pans  of  sulphuric  acid 
and  is  kept  at  a  partial  vacuum  of 
one  or  two  ounces,  the  acid  absorbs 
the  water  vapor  from  the  spray,  thus 
assisting  in  maintaining  the  vacuum 
and  lowering  the  temperature  of  the 
remainder  of  the  spray.  The  vapor- 
ization of  the  part  that  is  absorbed 
by  the  acid  requires  heat.  This 
heat  is  taken  from  the  liquid  of  the 
spray  that  is  not  absorbed,  conse- 
quently the  temperature  of  the  re- 
maining liquid  is  lowered.  In  a 
system  of  this  kind  a  temperature 
of  32  degrees  may  easily  be  ob- 
tained. The  water  or  brine  after 
cooling  is  then  circulated  through 
the  coils  of  the  cold  storage  room 
where  it  takes  up  the  heat  of  the  room  and  contents  and 
returns  to  the  vacuum  chamber  to  be  again  partially  evapo- 
rated and  cooled. 


Fig.  179. 


REFRIGERATION 


355 


211.  Cold  Air  System: — The  cold  air  system  is  used  prin- 
cipally on  ship  board.  Fig-.  180  shows  diagrammatically  the 
parts  and  the  operation  of  the  system.  The  cycle  has  four 
parts,  compression  in  one  of  the  cylinders  of  the  compressor, 
cooling  in  the  air  cooler  by  giving-  off  heat  to  the  cold  water 


Fig1.  180. 


thus  removing  the  heat  of  compression,  expansion  in  the  sec- 
ond cylinder  of  the  compressor  thus  cooling  the  air,  and 
refrigeration  in  the  cold  storage  room  where  the  heat  lost  dur- 
ing expansion  is  regained  from  the  articles  in  cold-storage. 
Cold  air  machines  work  at  low  efficiencies  because  of  the 
necessarily  large  cylinders  and  their  attendant  losses  due 
to  clearance,  heating  of  the  compression  cylinder,  snow  in 
the  expansion  cylinder  and  friction.  The  system  has  much 
to  recommend  it,  however,  since  it  is  extremely  simple,  occu- 
pies a  very  small  space  compared  with  other  systems  and 
uses  no  costly  gases,  chemicals  or  supplies. 

212.  The  Compression  and  the  Absorption  Systems  have 
in  common  this  fact — both  use  a  refrigerant,  i.  e.,  a  liquid  hav- 
ing a  comparatively  low  boiling  point.  Perhaps  the  most 
common  refrigerant  is  anhydrous  ammonia,  which  boils  at 
atmospheric  pressure,  at  28.5  degrees  below  zero  and  in 
doing  so  absorbs  as  latent  heat  573  B.  t.  u.  Table  59,  Ap- 
pendix, gives  further  properties.  Other  refrigerants  used 


356  MKATLVI    AND    VENTILATION 

to  a  lesser  extent  are  sulphur  dioxide.  S(>L.,  which  boils  at 
— 14  degrees  under  atmospheric  pressure  with  a  latent  heat 
of  162  B.  t.  u.  and  carbon  dioxide.  CO«,  which  boils  at  — 30 
degrees  under  a  pressure  of  182  pounds  per  square  inch 
absolute  with  a  latent  heat  of  140  B.  t.  u.  A  comparison  of 
the  temperatures  and  pressures  of  four  common  refriger- 
ants is  given  in  Table  64,  Appendix.  Pictet's  fluid  is  a  mix- 
ture of  97  per  rent,  sulphur  dioxide  and  :*  per  rent,  carbon 
dioxide. 

A  choice  of  a  universal  refrigerant  ran  scarcely  be  made 
because  of  the  varying  conditions  of  individual  plants.  The 
principal  difficulty  with  tlie  use  of  sulphur  dioxide  is  the 
fact  that  any  water  uniting  with  it  by  leakage  immediately 
produces  sulphurous  acid  with  its  corroding  action  upon  all 
the  iron  surfaces  of  the  system.  This  same  objection  holds 
also  for  Pictet's  fluid.  The  objections  to  the  use  of  carbon 
dioxide  are,  first,  its  comparatively  low  latent  heat,  and 
second,  the  high  pressure  to  which  all  parts  of  the  apparatus 
and  piping  are  subjected.  Pressures  of  from  300  to  !>oO 
pounds  per  square  inch  are  very  common.  Perhaps  the  worst 
charge  that  can  be  made  against  ammonia  as  a  refrigerant 
is  that  it  is  highly  poisonous  and  corrodes  metals,  particu- 
larly copper  and  copper  alloys.  However,  the  high  latent 
heat  of  ammonia,  together  with  the  fact  that  its  pressure 
range  is  neither  so  high  as  with  carbon  dioxide,  nor  so  low 
as  with  sulphur  dioxide,  are  perhaps  the  chief  reasons  for 
the  very  general  preference  for  ammonia  as  the  commercial 
refrigerant  in  compression  systems;  while  its  great  affinity 
for  and  solubility  in  water,  are  what  make  the  absorption 
system  a  possibility. 

213.  Compression  System: — Compression  machines  may 
work  well  with  the  use  of  any  one  of  the  four  refrigerants  of 
Table  64,  if  the  proper  pressures  and  temperatures  are  ob- 
served and  maintained.  The  common  refrigerant  for  this 
type  is,  however,  anhydrous  ammonia,  for  reasons  given 
above.  Fig.  131  shows  a  diagrammatic  sketch  of  the  com- 
pression system.  To  follow  the  closed  cycle  of  the  ammonia. 
start  with  a  charge  being  compressed  in  the  cylinder  of  the 
compressor.  From  this  it  is  conveyed  by  pipe  to  the  con- 
denser which,  being  cooled  by  water,  abstracts  the  latent 
heat  of  the  refri.uerant  and  condenses  it  to  a  liquid.  From 
the  condenser  the  liquid  refrigerant  is  conveyed  to  the 


REFRIGERATION 


357 


REFRIGERATOR 
ROOK  AT  50 


COOLING  VN*T£R  LlOUO  AMMONIA    EXf*NSION  VALVC    LIQU1°  Am°NIA  WARP   BRINE 

Fig.   181. 

pansion  valve  through  which  it  expands  into  the  evaporator 
or  brine  cooler.  In  changing  from  a  liquid  to  a  gas  in  the 
evaporator  it  absorbs  from  the  brine  an  amount  of  heat 
equivalent  to  the  heat  of  vaporization  of  the  ammonia. 
Upon  leaving  the  evaporator  the  refrigerant  is  again  ready 
for  the  cylinder  of  the  compressor,  thus  completing  the 
cycle. 


TEN  TON  AMMONIA  COMPRESSOR  UNIVERSITY  OF  NEBRASKA 

Fig.   182. 

If  the  refrigerant  is  ammonia,  the  compressor  is  com- 
monly of  the  vertical  type,  direct  connected  to  a  horizontal 
Corliss  engine  as  shown  in  Fig.  182.  This  type  of  com- 
pressor combines  the  high  efficiency  of  the  Corliss  engine 
with  the  vertical  type  of  compressor  which  is  probably  the 
best  type  for  reliable  service  of  valves  and  pistons.  The 
vertical  compressor  is  usually  sin^lo  ai'tin.u  with  water 


358 


HEATING  AND   VENTILATION 

AnnOMiA 


Fig.  183. 

jacketed  cylinders.  Horizontal  compressors  are  usually 
double  acting1,  as  shown  in  Fig.  183,  where  the  prime  mover 
is  a  direct  connected  electric  motor.  Poppet  valves  in  this 
type  are  placed  at  an  angle  of  30  degrees  to  45  degrees  with 
the  center  line  of  the  cylinder,  a  construction  made  neces- 


"I! !l! 'in I  \.JA>  |          ; 


Fig.  184. 

sary  by  space  restrictions  on  the  cylinder  heads.  Compres- 
sors for  other  refrigerants  are  commonly  of  these  same 
types,  the  main  difference  being  that  compressors  for  carbon 
dioxide  systems  are  nearly  always  two-stage  to  produce 
high  compressions.  The  intermediate  cooler  pressures  range 


REFRIGERATION 


359 


from  300  to  600  pounds  per  square  inch.  Horizontal  steam 
cylinders  in  tandem  with  the  compressor  cylinders  are  com- 
mon for  the  carbon  dioxide  systems  and  the  compressor  cyl- 
inders are  usually  single  acting". 

214.  Condensers  for  Compression  Systems  are  classi- 
fied under  four  heads,  atmospheric  condensers,  concentric 
tube  condensers,  enclosed  condensers  and  submerged  conden- 
sers. An  elevation  of  an  atmospheric  condenser  is  shown  in 
Fig.  184.  As  illustrated  it  consists  of  vertical  rows  of  pipes 
so  connected  by  return  bands  as  to  make  the  hot  refrigerant 
pass  through  each  pipe  beginning  at  the  top,  while  the  cold 
•water  main  at  the  top  of  the  row  furnishes  a  spray  of  water 
which  trickles  over  the  outside  of  the  pipes.  The  gas  on 
the  inside  of  the  pipes  is  thus  cooled  by  the  extraction  of 
the  quantity  of  heat  that  is  used  in  raising  the  temperature 
of  the  water  and  evaporating  a  part  of  it.  The  complete  con- 


Fig.   185. 

denser  may  consist  of  any  required  number  of  these  vertical 
rows,  placed  side  by  side,  each  row  properly  connected  to 
the  hot  gas  header  and  to  the  liquid  header. 

An  elevation  of  one  section  of  a  concentric  tube  condenser  is 
shown  in  Fig.  185.  The  arrows  show  the  paths  of  the  gas 
and  water.  As  in  the  atmospheric  type  the  gas  enters  at  the 


H  RATING  AND  VENTILATION 


The  cnelowd 


top  and  the  liquid  is  drawn  off  below.  In  its  descent  it 
passes  through  the  annular  space  between  the  two  concen- 
tric pipes  and  is  cooled  by  the  atmosphere  on  the  outside  of 
the  larger  pipes  and  by  the  water  circulating-  through  the 
inner  pipes.  This  condenser  has  the  advantage  over  the  sim- 
ple atmospheric  condenser  in  that  the  water  may  be  made  to 
have  an  upward  course  through  the  apparatus,  thus  bring- 
ing the  coldest  water  in  contact  with  the  pipes  carrying  the 
liquid  rather  than  with  the  pipes  carrying  the  hot  gas. 
Since  the  efficiency  of  the  plant  as  a  whole  is  very  largely 
dependent  upon  the  temperature  of  the  liquid  at  the  expan- 
sion valve  this  matter  of  the  "counter  flow"  of  the  cooling 
water  is  an  important  one.  For  the  medium  sized  and  large 
compression  systems  this  form  of  condenser  is  used  almost 
without  exception. 

fr  (Fig.  186)  is  very  similar  to  the  sur- 
face coil  condenser  in  steam  engine 
plants.  It  consists  of  a  cylindrical 
chamber  with  a  number  of  concen- 
tric pipe  spirals  connecting  a  hot 
•water  header  at  the  top  with  a  cold 
water  header  at  the  bottom  of  the 
cylinder.  The  pipes  of  the  spirals 
are  provided  with  stuffing  boxes 
where  they  pierce  the  upper  and 
lower  heads  of  the  cylinder.  With 
this  condenser  a  counter  flow  of 
the  water  is  used,  the  cold  water  en- 
tering the  bottom  of  the  coils  and 
flowing  upward,  so  that  the  liquid  re- 
frigerant at  the  bottom  of  the  cylin- 
der is  very  near  the  temperature  of 
the  incoming  water. 

A  submerged  condenser,  as  the  name 
implies,  contemplates  a  rather  large 
body  of  water  below  the  surface  of 
which  there  is  submerged  a  coil  for 
circulating  the  hot  refrigerant.  Fig. 
187  shows  a  section  of  such  a  con- 
Fig,  186  denser.  The  hot  gas  enters  at  the 

top   fitting   of   the    coil   and   leaves   at 
lower  fitting.     Cold  water  is  constantly  flowing  in  at  the  bot- 


REFRIGERATION 


361 


torn  of  the  tank  and  leaving  by  the  overflow  at  the  top,  being 
heated  as  it  rises.  The  form  of  the  coil  is  usually  spiral, 
although  this  condenser  may  be  built  with  coils  of  the  re- 
turn bend  type  when 
larger  surface  is  re- 
quired. Only  the  small- 
er compression  plants 
use  the  enclosed  or  the 
submerged  type  of  con- 
denser. 

In  general,  con- 
densers may  be  consid- 
ered vital  factors  in 
the  economy  of  com- 
pression plants.  They 
must  be  reliable  in 
service  and  economical 
in  operation,  and  must 
be  so  designed  and 
proportioned  that  they 
will  deliver  liquid  re- 
frigerant within  five 
degrees  of  the  tem- 
perature of  the  incom- 
ing cooling  water.  A 
condenser  should  pre- 
sent all  joints,  particularly  those  holding  the  refrigerant,  to 
plain  view  for  easy  inspection  and  repair.  Since  it  is  the  func- 
tion of  the  condenser  to  dissipate  the  heat  of  the  refrigerant 
gas,  it  is  not  uncommon  to  install  it  upon  the  roof  or  out- 
side the  building  in  some  cool  place.  This  is  especially  true 
where  the  atmospheric  or  the  concentric  tube  types  are 
used.  In  such  positions  the  heat  radiated  by  the  condenser 
is  not  given  back  to  the  rooms  and  piping  systems.  In  addi- 
tion, the  cooling  action  of  the  atmosphere  assists  in  making 
the  system  more  efficient. 


Fig.  137. 


215.  Evaporators  for  compression  systems  may  be  con- 
sidered as  condensers,  reversed  in  action  but  very  similar 
in  form.  If  the  refrigerating'  effect  is  accomplished  by  the 
brine  cooling  system  an  evaporator  of  some  type  will  be 


362 


HEATING  AND  VENTILATION 


necessary,  but  if  the  refrigeration  is  accomplished  by  circu- 
lating the  expanding  refrigerant  itself,  no  evaporator  is  re- 
quired. Evaporators,  or  brine  coolers,  may  be  classified 
according  to  the  method  of  construction,  as  shell  coolers  and 
concentric  tube  coolers. 

The  shell  cooler  takes  various  forms.  One  is  shown  by 
Fig.  186,  being  in  effect  an  enclosed  condenser  with  brine 
instead  of  cold  water  circulating  in  the  coils.  The  heat  of 
the  brine  is  transferred  to  the  cool  liquid  refrigerant,  caus- 
ing the  refrigerant  to  evaporate  and  take  from  the  brine 
an  amount  of  heat  equal  to  the  latent  heat  of  the  refriger- 
ant. The  proper  height  to  which  the  liquid  refrigerant 
should  be  allowed  to  rise  in  the  evaporator  is  a  very  much 
disputed  point,  some  old  and  experienced  operators  claim- 
ing greatest  efficiency  when  about  one-third  of  the  cooling 


Fig.  188. 

surface  is  covered  with  liquid  refrigerant  leaving  two- 
thirds  to  be  covered  with  gaseous  refrigerant.  Others  claim 
that  the  entire  surface  should  be  covered  or  "flooded"  with 
liquid  refrigerant.  These  points  of  view  give  rise  to 
the  two  terms  dry  systems  and  flooded  systems.  Of  late  years 
the  flooded  systems  are  gaining  somewhat  in  favor,  a  sepa- 
rator being  installed  between  the  evaporator  and  the  com- 
pressor to  prevent  any  liquid  being  drawn  into  the  com- 
pressor cylinder.  This  separator  drains  any  liquid  which 
may  collect  therein,  back  into  the  evaporator.  In  the  flooded 
system  the  brine  cooler  more  commonly  takes  the  form 
shown  in  Fig.  188,  where  at  the  end  A  D  of  the  brine  tank 
ABCD  is  shown  the  flooded  cooler  E.  This  cooler  consists 


REFRIGERATION  3(53 

of  a  boiler  shell  filled  with  tubes,  the  brine  circulating 
through  the  inside  of  the  tubes  while  the  interior  of  the 
large  shell  is  nearly  or  quite  filled  with  liquid  refrigerant. 
Concentric  tube  brine  coolers  are  made  of  piping  very  similar 
in  principle  to  that  shown  in  Fig.  185,  with  the  exception 
that  instead  of  two  concentric  pipes,  three  are  more  com- 
monly employed.  The  brine  circulates  through  the  inner- 
most of  the  three  and  through  the  outermost,  while  the 
annular  space  between  the  smallest  pipe  and  the  middle 
pipe  is  traversed  by  the  liquid  refrigerant.  In  this  way 
the  annular  space  filled  with  refrigerant  has  brine  on  both 
sides  and  the  cooling  of  the  brine  is  very  rapid.  The  numer- 
ous joints  in  this  cooler  present  a  constant  source  of  trouble. 
Salt  brine  will  usually  freeze  in  the  inner  pipe,  so  that  cal- 
cium chloride  brine  must  be  used. 

A  choice  of  evaporators  or  coolers  depends  mainly  upon 
whether  the  plant  is  to  run  continuously  or  intermittently. 
When  run  continuously  only  a  small  amount  of  brine  is 
required,  and  this,  when  cooled  quickly  and  circulated 
quickly,  would  call  for  a  concentric  tube  cooler.  When  run 
intermittently  a  much  larger  body  of  brine  is  desirable  so 
as  to  remain  cool  longer  during  the  night  hours  when  the 
plant  is  not  operating.  For  this  condition  a  shell  type 
cooler  would  probably  be  preferred. 

In  addition  to  the  condensers  and  evaporators  that  were 
described  in  detail,  there  are  to  be  found  on  the  well  equip- 
ped compression  system  the  following  pieces  of  apparatus 
which  will  be  mentioned  and  described  only  briefly.  An  oil 
separator  is  commonly  found  in  the  line  connecting  the  con- 
denser with  the  compressor.  This  is  simply  a  large  cast 
iron  cylinder  with  baffle  plates  to  separate  the  oil  from  the 
ammonia.  Since  the  oil  is  heavier  than  the  ammonia  it  set- 
tles to  the  bottom  and  may  be  drawn  off.  An  ammonia  scale 
strainer  is  often  found  just  before  the  compressor  intake. 
Small  purge  valves  are  located  at  all  high  points  in  the 
system  for  the  purpose  of  exhausting  the  foul  gases  or  the 
air  which  may  collect  in  the  system.  Such  a  purge  con- 
nection is  shown  on  the  right  end  of  the  upper  coil  in 
Fig.  184. 

216.  Pipes,  Valves  and  Fittings  for  compressor  refriger- 
ant piping  are  considerably  different  from  the  standard  types. 
If  the  refrigerant  is  ammonia,  no  brass  enters  into  the  de- 


364  HEATING  AND  VENTILATION 

sign  of  any  part  of  the  piping  or  auxiliaries  traversed  by  the 
ammonia.  The  operating-  principles  of  all  valves  are  the 
same  as  standard  ones  but  they  are  made  heavier  and  en- 
tirely of  iron,  or  iron  and  aluminum.  The  common  threaded 
joint  used  on  all  standard  fittings  is  replaced  in  ammonia 
systems  by  the  bolted  and  packed  joint.  It  is  not  within  the 
scope  of  this  work  to  go  into  these  details  further  than  to 
/ —  — N  give  a  section  of  an  ammonia  expan- 

'      sion  valve  (Fig.  189)  and  a  section  of  a 

typical  ammonia  joint   (Fig.  190). 


Fig.  189.  Fig.  190. 

217.  Absorption  System: — As  stated  in  Art.  190,  the 
great  affinity  of  ammonia  gas  for  water  and  its  solubility 
therein,  are  what  make  the  absorption  system  a  possibility, 
and  give  it  the  name  as  well.  At  atmospheric  pressure  and 
50  degrees  temperature  one  volume  of  water  will  absorb 
about  900  volumes  of  ammonia  gas.  At  atmospheric  pres- 
sure and  100  degrees  temperature  one  volume  of  water 
will  absorb  only  about  one-half  as  much  gas,  or  450  vol- 
umes. If  then,  one  volume  of  water  is  saturated  at  50  de- 
grees with  ammonia  gas  and  heated  to  100  degrees  there 
will  be  liberated  about  450  volumes  of  ammonia  gas.  Hence 
it  is  evident  that  a  stream  of  water  may  be  used  as  a  con- 
veyor of  ammonia  gas-  from  one  place  or  condition  to  an- 
other, say  from  a  condition  of  low  temperature  and  pres- 
sure where  the  absorbing  stream  of  water  would  be  cool,  to 
a  condition  of  high  temperature  and  pressure,  where  the 
gas  would  be  liberated  by  simply  heating  the  water.  It  will 
be  noticed  that  the  gas  has  been  transferred  as  a  liquid 
without  a  compressor  or  any  compressive  action,  by  pump- 


REFRIGERATION 


365 


ing  a  stream  of  water  of  approximately  one-four  hundred 
and  fiftieth  of  the  volume  of  the  gas  transferred.  This,  in 
the  abstract,  is  the  method  employed  in  the  absorption 
system  to  convey  the  ammonia  gas  from  the  relatively  low 
temperature  and  pressure  of  the  evaporator  to  the  high 
temperature  and  pressure  at  the  entrance  of  the  condenser. 
The  absorption  system,  when  closely  compared  in  prin- 
ciples of  operation  to  the  compression  system,  differs  only 
in  one  respect,  namely,  the  absorption  system  replaces  the 
gas  compressor  by  the  strong  and  weak  liquor  cycle.  As 

shown  in  Fig.  191,  both  sys- 
tems   have    arrangements    of 
condenser,     expansion     valve 
and  evaporator  that  are  iden- 
tical,  hence   the   part    of   the 
cycle  through  these  need  not 
be   considered.     The   problem 
of  completing  the  cycle  from 
evaporator       t  o       condenser, 
however,  is  solved  quite  dif- 
ferently in  the  two  systems. 
In    the    compression    system 
(upper  diagram)    the   evapo- 
rator   delivers    the    expanded 
gas  to  the  compres- 
sor,     from      which, 
under      high      pres- 
sure   and    tempera- 
ture,  it  is  delivered 
to      the      condenser 
and      the     cycle      is 
completed.      In    the 
absorption       system 
(lower     diagram) 
the    evaporator    de- 
livers the  expanded 
gas  to  an  absorber, 
in     which     the     gas 
comes      in      contact 

CfCLt  "  with  a  spray  of  so- 

Fi&-  191-  called     weak     liquor, 

consisting    of    water    containing    about    15    to    20    per    cent. 


366  HEATING  AND  VENTILATION 

of  anhydrous  ammonia.  The  weak  liquor  absorbs  the 
ammonia  gas  through  which  the  liquor  is  sprayed  and  col- 
lects in  the  upper  part  of  the  absorber  as  strong  liquor,  contain- 
ing about  twice  as  much  anhydrous  ammonia  as  the  weak 
liquor,  x>r  30  to  35  per  cent.  From  here  it  is  pumped  through 
the  exchanger  (which  will  be  ignored  for  the  present)  into 
the  generator  at  a  pressure  of  about  170  pounds  per  square 
inch  gage.  In  the  generator  heat  is  supplied  by  steam  coils 
immersed  in  the  strong  liquor.  As  this  liquor  is  heated  it 
gives  up  about  half  of  the  contained  ammonia  gas  which 
rises  and  passes  from  the  generator  to  the  condenser,  thus 
completing  the  ammonia  or  primary  cycle,  while  the  weak 
liquor  flows  from  the  bottom  of  the  generator  through  the 
exchanger  and  pressure  reducing  valve  back  to  the  absorber, 
thus  completing  the  secondary  or  liquor  cycle. 

In  general  then,  the  absorption  system  uses  two  cycles, 
that  of  the  ammonia  and  that  of  the  liquor,  the  paths  of  the 
two  cycles  being  coincident  from  the  absorber  to  the  gen- 
erator. The  liquor  pump  serves  to  keep  both  cycles  in  mo- 
tion. The  pump  creates  the  pressure  for  both  cycles  and 
the  expansion  valve  and  the  reducing  valve  reduce  the 
pressure  respectively  for  the  ammonia  cycle  and  the  liquor 
cycle.  The  exchanger  does  not  mix  or  alter  the  condition  of 
the  two  streams  of  liquor  passing  through  it,  for  its  only 
function  is  to  bring  these  two  streams  close  enough  that 
the  heat  of  the  weak  liquor  from  the  generator  may  be  trans- 
ferred to  the  strong  liquor  going  to  the  generator.  Stated  in 
other  words,  the  exchanger  heats  the  strong  liquor  by  cool- 
ing the  weak  liquor,  thus  affecting  a  saving  of  heat  which 
would  otherwise  be  lost,  since  the  weak  liquor  must  be 

£ 

cooled  before  it  is  ready  to  properly  absorb  the  gas  in  the 
absorber. 

218.  An  Elevation  of  an  Absorption  System  with  the 
elements  piped  according  to  what  is  considered  best  prac- 
tice is  shown  in  Fig.  192.  Starting  at  the  expansion  valve, 
the  ammonia  (liquid,  gas  or  gas  in  solution)  passes  in  order 
through  these  pieces  of  apparatus:  the  evaporator,  the  ab- 
sorber, the  liquor  pump,  the  chamber  of  the  exchanger  or  the 
coil  of  the  rectifier,  the  generator,  the  chamber  of  the  recti- 
fier and  the  condenser  back  to  the  expansion  valve.  At  the 
same  time  the  liquor  used  to  absorb  the  gas  travels  in  order 
through  these  pieces:  the  absorber,  the  liquor  pump,  the 


REFRIGERATION 


367 


chamber  of  the  exchanger  or  the  coil  of  the  rectifier,  the 
generator,  the  pressure  reducing  valve  and  the  coil  of  the 
exchanger  back  to  the  absorber.  The  method  of  pipe  connec- 
tion shown  is  a  very  common  one  although  some  varia- 
tion may  be  found,  especially  in  the  continued  use  of  cool- 
ing water  in  consecutive  pieces  of  apparatus.  As  shown, 
the  cooling  water  is  first  used  in  the  condenser.  This  will 
be  found  so  in  all  plants.  From  the  condenser  the  cooling 
water  may  next  be  taken  to  the  absorber,  as  shown  in  the 
sketch,  or  it  may  be  used  in  the  rectifier  coil  instead  of  the 
strong  liquor.  In  recent  years  the  practice  of  by-passing 
a  certain  amount  of  the  cool,  strong  liquor  from  the  pump 
through  the  rectifier  is  gaining  in  favor.  Fig.  192  shows 
a  plant  having  bent  coil  construction.  Plants  are  also  built 
having  a  straight  pipe  construction,  where  all  coil  surfaces 
shown  are  replaced  by  straight  pipes,  the  condenser  being 
usually  of  the  concentric  tube  atmospheric  type  and  the 
evaporator  being  also  of  the  concentric  tube  brine  cooler 
type,  as  mentioned  under  compression  systems.  Both  types 
of  absorption  plants  are  found  in  use. 


Fig.  192. 


368 


HEATING  AND  VENTILATION 


219.  Generators  are  classified  as  horizontal  and  verti- 
cal. Fig1.  193  shows  a  horizontal  type  generator,  with  the 
analyzer  and  exchanger,  and  Fig.  194  shows  the  vertical 
type,  also  with  the  analyzer.  The  horizontal  type  may  have 
one  or  more  horizontal  cylinders  equipped  with  steam  coils. 
The  analyzer,  which  may  be  considered  as  an  enlarged  dome 
of  the  generator,  is  used  to  condense  the  water  vapor  which 
rises  from  the  surface  of  the  liquid  in  the  generator.  To 
do  this  the  analyzer  has  a  series  of  horizontal  baffle  plates 
through  which  the  incoming  cool,  strong  liquor  trickles 


Fig.   193. 

downward  while  the  heated  mixture  of  ammonia  gas  and 
water  vapor  passes  upward  through  interstices.  In  this 
way  the  strong  liquor  gradually  cools  the  ascending  water 
vapor  and  condenses  much  of  it  on  the  surfaces  of  the 
baffle  plates. 

220.  Rectifiers  are  arrangements  of  cooling  surface 
designed  to  thoroughly  dry  the  gas  just  before  it  passes 
into  the  condenser.  This  is  accomplished  by  presenting  to 
the  hot  product  of  the  generator  just  enough  cooling  sur- 
face to  condense  the  water  vapor  without  condensing  any  of 


CF* 


Fig.  194. 


REFRIGERATION  369 

the    ammonia    gas.      Rectifiers    are 
very   similar   in   general   design   to 

•*  the  various  types  of  condensers, 
there  being  atmospheric,  concen- 
tric tube,  enclosed  and  submerged 
rectifiers  just  as  there  are  these 
same  type  of  condensers,  each  de- 
scribed under  the  head  of  con- 
densers for  compression  systems. 
Rectifiers  may  save  heat  by  the 
arrangement  shown  in  Fig.  192, 
where  the  heat  abstracted  from  the 
water  vapor  is  given  to  the  cool, 
strong  liquor  before  entering  the 
generator.  As  shown,  the  strong 
liquor  may  be  divided,  part  pass- 
ing through  the  rectifier  and  part 
through  the  exchanger,  or  the 
strong  liquor  may  all  go  through 
the  exchanger  first  and  then 
through  the  rectifier.  Where 
strong  liquor  is  so  used,  the  recti- 
fier is  always  of  the  enclosed 
type.  Rectifiers  using  water  as 
the  cooling  medium  are  often 
called  dehydrators,  the  term  rec- 
tifier being  more  properly  used 
when  the  cooling  medium  is  the 
strong  liquor. 

221.  Condensers  for  absorption 
systems  do  not  differ  in  design 
from  those  used  for  compression 
systems.  The  same  types  are  used, 
and  in  the  same  manner,  the  sur- 
face being  somewhat  less  due  to 
the  precooling  effect  of  the  recti- 
fiers or  dehydrators.  As  a  gen- 
eral statement,  it  is  claimed  that 
from  20  to  25  per  cent,  less  surface 
is  required  in  the  condenser  for  an 
absorption  machine  than  is  re- 
quired in  one  for  a  compression 
machine. 


370  HEATING  AND  VENTILATION 

222.  Absorbers  may  be  classified  as  dry  absorbers,  wet 
absorbers,  atmospheric  absorbers,  concentric  tube  absorb- 
ers and  horizontal  and  vertical  tubular  absorbers.  In  the 
dry  absorber,  the  top  section  of  which  is  shown  in  Fig.  195, 

the  weak  liquor  enters  at  the 
middle  of  the  top  header  and 
is  sprayed  upon  a  spray  pan, 
from  which  it  drips  downward 
over  the  coils.  The  gas  enters 
as  shown,  part  being  delivered 
above  the  spray  plate,  so  as  to 
come  into  contact  with  the 
spray  and  the  larger  part  being 
taken  downward  through  the 
central  pipe  to  a  point  near  the 
bottom  of  the  absorber,  from 
which  point  it  flows  upward 


Fig.195. 


against  the  descending  weak  liquor  by  which  it  is  absorbed. 
As  the  gas  is  dissolved  by  the  weak  liquor  the  heat  of  ab- 
sorption is  given  off,  and  taken  up  by  the  cooling  water  in 
the  coils.  The  result  is  a  strong  liquor  which  collects  in 
the  absorber  ready  to  be  delivered  to  the  pump. 

The  ivet  absorber,  on  the  contrary,  has  practically  the 
whole  body  filled  with  weak  liquor  and  the  ammonia  gas 
enters  near  the  bottom,  bubbling  up  through  the  weak 
liquor  thus  saturating  it.  Various  baffle  plates  with  fine 
perforations  break  up  the  gas  into  small  bubbles  thus  aid- 
ing in  presenting  a  large  surface  of  gas  to  the  liquor 
which,  as  it  becomes  saturated  and  lighter,  rises  to  the  top 
of  the  body  of  the  absorber  and  is  ready  to  be  drawn  off  by 
the  pump.  Instead  of  spiral  cooling  coils,  this  type  is  often 
made  with  straight  cooling  tubes  inserted  between  two  tube 
sheets,  boiler  fashion.  This  straight  tube  construction  is 
much  simpler  and  cheaper,  and  much  more  easily  cleaned 
than  the  spiral  type.  It  is  favored  by  some  on  this  account, 
especially  where  the  cooling  water  has  a  tendency  to  form 
scale. 

Atmospheric  absorbers  resemble  atmospheric  condensers  of 
the  single  tube  type.  The  ammonia  gas  and  weak  liquor 
enter  the  bottom  through  a  fitting  commonly  called  a  mixer, 
and  the  two  flow  upward  through  the  inside  of  the  pipe 
while  the  cooling  water  is  in  contact  with  the  outside  thus 
taking  up  the  heat  of  absorption  generated  within  the  pipes. 


REFRIGERATION  371 

Concentric  tube  absorbers  are  very  similar  in  design  to  con- 
centric tube  condensers,  the  cooling-  water  passing  through 
the  central  tube  and  the  weak  liquor  and  expanded  gas  en- 
tering at  the  bottom  of  the  annular  space  and  circulating  to 
the  top,  absorption  taking  place  on  the  way.  Because  of  the 
small  capacity  of  the  last  two  mentioned  absorbers,  it  is 
necessary  to  use  with  them  an  aqua  ammonia  receiver  be- 
tween the  absorber  and  the  ammonia  pump,  to  act  as  a 
reservoir  for  storing  a  reserve  supply  of  the  strong  liquor. 

Horizontal  and  vertical  tubular  absorbers  are  those  in  which 
the  cooling  surface  is  composed  of  straight,  horizontal  or 
vertical  tubes  inserted  between  tube  sheets,  the  cooling 
water  flowing  inside  the  tubes  and  the  absorption  taking 
place  within  the  drum  or  body  of  the  absorber. 

223.  Exchangers   may   be   of   two   types,    the   shell   type 
or  the  concentric  tube  type.     The  shell  type,  as  the  name  im- 
plies,   is   composed   of  a   main   body   or  shell   through  which 
circulates   the    strong   liquor   to   be    heated   and   within   this 
shell  is  a  coil  or  other  arrangement  of  heating  pipes  through 
which  the  hot,  weak  liquor  flows.     Fig.   192   shows  the  ele- 
mentary   arrangement    of    such    an    exchanger.      Concentric 
tube  exchangers  are  used  on  large  plants.     They  are  similar 
in   every   way   to   the   concentric   tube   condensers   shown    in 
Fig.    185,   with   the    exception   that   larger   pipes   are   needed 
for  the  exchangers.     The  cold,  strong  liquor  is  usually  car- 
ried through  the  pipes  and  the  hot,  weak  liquor  through  the 
annular    space.      The    great    advantage    of   this    type    of   ex- 
changer   is   the    same    as   that    of  the    concentric   tube   con- 
denser, namely,  the  counter  flow  of  the  two  streams.     With 
this  arrangement  the  total  transfer  of  heat  is  a  maximum, 
for  which   reason   this   type   of  exchanger   is  generally   pre- 
ferred. 

224.  Coolers    for    the    weak    liquor   are    often    found    in 
plants.     This  piece  of  apparatus  is  not  indicated  in  Fig.  192. 
It  is  usually  installed  as  the  lower  three  coils  of  the  atmos- 
pheric   condenser,    and    hence    is    simply    a    small    condenser 
used  to  further  cool  the  weak  liquor  just  before  its  entrance 
into  the  absorber.     With  a  counter  flow,  concentric  tube  ex- 
changer a  weak  liquor  cooler  is  seldom  found  necessary. 

225.  The  Pump  used  in  absorption  systems  to  raise  the 
pressure  of  the  strong  aqua  ammonia  may  be  steam  driven, 
electric   driven   or   belt   driven,   as   best   suits   the   particular 


372  HEATING  AND  VENTILATION 

plant  conditions.  The  power  required  by  this  piece  of  appa- 
ratus is  about  one  horse  power  per  20  to  25  tons  of' refriger- 
ation capacity. 

226.  Compression  Systems  and  Absorption  Systems  Com- 
pared:— A  comparison   drawn  between  the  compression   sys- 
tem   and    the    absorption    system    brings    out    the    following 
facts:     The  compression  system  depends  fundamentally  upon 
the  transferring  of  heat  energy  into  mechanical  energy  and 
vice  versa,  with  the  attendant  heavy  losses.     The  absorption 
system    merely    transfers    heat    from    one    liquid    to    another. 
This  is  a  process  which  is  attended  by  only  moderate  losses. 
The    compression    system    is   comparatively    simple,    its    pro- 
cesses readily  understood  and  its  machinery  easily   kept   in 
good  running  order.     The  absorption  system   is  complicated 
with  a  greater  number  of  parts,  its  processes  are  often  not 
thoroughly  understood  by  those  in  charge  and  its  machinery 
is  likely  to  become  inefficient  because  heat  transferring  sur- 
faces are   allowed   to   become   dirty.     For  these   reasons   the 
attendance  necessary  upon  an  absorption  plant  must  be  of  a 
higher   order   than   that   necessary   for   a   compression   plant. 

227.  Circulating  Systems: — The  refrigerating  effect  pro- 
duced by  either  one  of  the  two  systems  may  be  delivered  to 
the  place  of  application  in  two  ways.     The  first  is  the  brine 
circulation    method    wherein    a    brine    cooler    is    used    through 
which  the  brine  flows  causing  the  evaporation  of  the  liquid 
refrigerant  and  the  cooling  of  the  brine.     This  cold  brine  is 
then  circulated  through  pipes  to  the  place  where  refrigera- 
tion is  desired.     Fig.  188  shows  an  evaporator  placed  in  one 
end  of  a  large  brine  tank.     The  refrigerating  effect  is  car- 
ried to  the  cans  of  water  by  the  circulation  of  this  body  of 
brine  through  the  evaporator  and  out  past  the  cans,  the  cir- 
culation  through   the   chanriels   shown   being   maintained   by 
the  pump.     Brine,  commonly  used  for  such  work,  is  made  by 
dissolving  calcium   chloride  in   water.     A  20   per  cent,   solu- 
tion  is   generally   used.      Salt   brine   is   used   to   some   extent 
but  it  has  many  disadvantages  compared  with  calcium  brine. 
The  second  method  is  the  direct  circulation  method  wherein  the 
liquid  refrigerant  is  conveyed  to   the  place   to  be  cooled,   is 
passed    through    an    expansion    valve    and    then    circulated 
through  coils  in  the  space  to  be  refrigerated,  changing  into 
gaseous    form    as    fast    as    it    can    absorb    enough    heat.      If 
ammonia  is  the  refrigerant  the  direct  circulation  is  not  often 
favored  because  of  its  highly  penetrative   nature   and  odor, 


REFRIGERATION 


373 


even  a  leak  so  small  as  to  escape  detection  being-  sufficient 
to  fill  the  refrigerated  space  with  the  odor,  which  many 
food  stuffs  will  absorb. 

228.  There  are  Three  Methods  Employed  for  Maintain- 
ing Low  Temperatures  in  storage  and  other  rooms.  The 
first  is  by  direct  radiation  where  the  pipes  are  placed  within 
the  room  and  the  refrigerant  is  circulated  through  them. 
This  is  the  oldest,  simplest  and  cheapest  system  to  install. 
In  this  the  proper  location  and  arrangement  of  the  pipes  are 
essential  to  the  most  efficient  operation.  Since  the  tempera- 
ture to  be  maintained  in  a  storage  room  depends  upon  the 
products  to  be  kept  in  the  room,  it  may  be  necessary  to  have 
a  considerable  range  of  temperature.  It  is  desirable  to  have 
the  pipes  arranged  as  coils  in  two  or  three  sets,  each  being 
valved  so  that  the  amount  of  refrigerant  being  circulated 
may  be  increased  or  decreased  as  the  temperature  of  the 
stored  product  may  require. 

The  pipes  should  be  set  out  from  the  wall  several  inches 
to  give  free  air  circulation  and  keep  the  frost  that  collects 
on  them  from  coming  in  contact  with  the  wall.  The  coils 
should  be  so  placed  that  the  temperature  of  all  parts  of  the 
room  may  be  kept  as  nearly  uniform  as  possible.  Some 
products  keep  as  well  in  still  air  as  when  it  is  in  motion,  but 
others,  such  as  fruits,  eggs,  cheese,  etc.,  are  better  pre- 
served when  the  air  is  circulated.  Circulation  may  be  ef- 
fected in  a  room  piped  for  direct  radiation  by  putting  aprons 
over  the  coils  as  shown  in  Fig.  196.  These  aprons  consist  of 

12  inch  boards  D  nailed  to 
studding  E  and  the  whole 
fastened  to  the  coils,  the 
studding  serving  to  keep  the 
boards  from  coming  into 
contact  with  the  pipe  coils. 
A  false  ceiling  F  is  placed  a 
few  inches  below  the  ceiling 
of  the  room  so  that  the 
warm  air  flows  toward  the 
pipes  and  over  them,  drop- 
ping to  the  floor  and  passing 
out  under  the  lower  edge  of 
the  apron  into  the  room, 
drip  pans  should  be 


Fig.  196. 
Wherever  direct  radiation  is    used 


374 


HEATING  AND  VENTILATION 


placed  directly  unde-rneath  the  coils  in  order  to  catch  and 
drain  off  the  water  when  the  coils  are  cut  out  and  the  frost 
melts.  This  water  should  be  drained  into  a  receptacle  that 
can  be  easily  emptied  when  filled. 

The  second  method  of  room  cooling  is  by  indirect  radiation. 
Let  Fig".  197  represent  a  section  of  a  storage  building.  The 
essential  parts  of  the  cooling  system  are, 
a  bunker  room  AC,  in  the  top  part  of  the 
building,  containing  the  cooling  coils 
B,  a  series  of  ducts  on  either  side  of  the 
building,  so  arranged  that  the  air  after 
passing  over  the  cooling  coils,  drops 
downward.  These  ducts  are  provided 
with  dampers  for  admitting  as  much  of 
the  cold  air  to  the  rooms  as  is  desired. 
On  becoming  warmed  this  air  is  crowded 
out  on  the  opposite  side  of  the  room  into 
the  ducts  K  and  rises  to  the  bunker- 
room  where  it  is  again  cooled  by  passing 
over  the  coils.  By  the  use  of  the  damp- 
ers the  cold  air  may  be  cut  off  from  any 
room  or  admitted  in  large  quantities 
thus  making  it  an  easy  matter  to  main- 
tain the  temperature  at  any  point  de- 
sired. The  ducts  leading  the  air  from 
the  rooms  should  be  25  per  cent,  larger 
than  the  ones  leading  to  the  rooms  and 
the  latter  should  have  about  three  square 
inches  cross-section  per  square  foot  of 
floor  area  in  rooms  having  a  ten  foot 
ceiling. 

The    third    method    is    by    means    of    a 

plenum  system  of  air  circulation,  Fig.  198.  The  arrangements 
are  quite  similar  to  those  of  the  plenum  system  for  heating, 
except  that  the  heating  coils  are  replaced  by  the  refrigerat- 
ing coils.  The  air  required  for  ventilation  is  blown  over  the 
coil  surface,  erected  in  a  coil  or  bunker  room,  over  which, 
oftentimes,  cold  water  is  sprayed.  This  not  only  washes 
the  air  but  tends  to  lower  its  temperature.  If  ammonia  is 
used  as  a  refrigerant,  brine  is  circulated  in  the  coils,  but  if 
carbon  dioxide  is  used  direct  expansion  is  employed,  thus 


Fig.  197. 


REFRIGERATION 


375 


Fig.  198. 


dispensing-  with  the  use  of 
brine.  The  principal  advan- 
tage of  the  plenum  system  of 
cooling  is  that  a  positive  cir- 
culation of  air  may  be  main- 
tained in  any  room  even  though 
the  bunker  room  be  placed  on 
the  first  floor  or  in  the  base- 
ment of  the  building.  This  is 
the  system  used  in  large  build- 
ings that  are  cooled  during  the 
summer  as  well  as  heated  dur- 
ing winter,  in  factories  where  changes  of  temperature  seri- 
ously affect  the  product,  as  in  chocolate  factories,  in  fur 
storage  rooms,  in  drying  the  air  before  it  is  blown  into  blast 
furnaces  and  in  the  solution  of  many  other  important  eco- 
nomic problems. 

229.  Influence  of  the  Dew  Point: — In  cooling  a  building 
by  means  of  a  plenum  refrigerating  system,  great  trouble 
is  experienced  with  the  formation  of  ice  on  the  coils.  For 
example,  suppose  such  a  cooling  system  on  a  hot  summer 
day  is  taking  in  air  at  90  degrees  temperature  and  85  per 
cent,  humidity.  If  this  air  is  cooled  only  ten  degrees  (see 
chart,  page  29),  it  will  have  reached  its  dew  point  and  as 
the  cooling  continues  will  deposit  frost  and  ice  on  the  coils 
from  the  liberated  moisture,  the  air  meantime  remaining  at 
the  saturation  point  and  being  so  delivered  to  the  rooms.  The 
undesirable  feature  of  delivering  saturated  air  to  the  rooms 
may  be  avoided  by  cooling  only  part,  say  half  of  the  air 
stream,  considerably  lower  than  the  final  temperature  de- 
sired, and  then  mixing  it  with  the  other  half,  which  is 
drier,  before  delivering  it  to  the  rooms.  The  troublesome 
coating  of  ice  and  frost  on  the  pipes  may  be  avoided  by 
combining-  the  cooling  system  with  the  air  washing  system 
and  using  a  brine  spray  instead  of  water  for  washing  the 
air  during1  cooling.  The  brine,  which  freezes  at  a  very  low 
temperature  compared  with  water,  plays  over  the  cooling 
coils,  and  cleans  both  coils  and  air.  The  brine  should  pref- 
erably be  a  chloride  brine.  A  modification  of  this  method  of 
avoiding  ice  and  frost  is  to  provide  pans  above  the  coils 
and  fill  them  with  lumps  of  calcium  chloride.  The  pans 
have  perforations  so  arranged  that  as  the  strong  chloride 


376 


HEATING  AND  VENTILATION 


solution  forms  (due  to  the  deliquescence  of  the  salt)  it 
trickles  down  over  the  pipes  and  holds  the  freezing  point 
of  any  collecting-  moisture  far  below  the  temperature  of  the 
coils.  A  sketch  of  this  arrangement  is  shown  in  Fig.  195, 
which  has  the  disadvantage  of  the  clumsy  handling  of  the 
calcium  chloride.  Plants  operating  only  during  the  day,  as  for 


Fig.   199. 

instance,  auditoriums,  commerce  chambers,  etc.,  often  have 
no  equipment  for  preventing  the  accumulation  of  frost  and 
ice,  it  being  allowed  to  form  during  the  short  period  of  use 
and  to  melt  during  the  period  of  rest. 

230.  Pipe  Line  Refrigeration: — In  a  number  of  the 
larger  cities  refrigeration  is  furnished  to  such  places  as 
cold  storage  rooms,  restaurants,  hotels,  auditoriums,  etc., 
by  a  conduit  system  or  central  station  system.  The  length 
of  the  mains  in  the  various  cities  where  used,  ranges  from 
a  few  hundred  feet  to  twenty  miles  and  the  circulating 
medium  employed  is  either  liquid  ammonia  or  brine.  In  the 
ammonia  system  two  pipes  are  used,  one  carrying  the  liquid 
ammonia  to  the  place  desired  and  the  other  returning  it 
after  expansion  to  the  central  station.  When  brine  is  used 
it  is  good  practice  to  circulate  it  at  from  12  to  15  degrees  F. 
Occasionally  the  conduits  carry  three  parallel  pipes,  two  of 


REFRIGERATION 


37' 


which  are  for  circulating  the  brine  and  the  third  is  for 
emergency  cases.  The  line  should  be  divided  into  sections, 
with  valves  and  by-passes  so  arranged  that  a  defective  sec- 
tion could  be  repaired  without  interfering  with  the  other 
parts.  All  valves  should  be  readily  accessible  and  all  high 
points  in  the  system  should  be  equipped  with  purge  valves. 
The  service  pipes  should  be  two  inches  in  diameter  and  well 
insulated. 

Either  the  ammonia  absorption  or  compression  system 
may  be  used  for  cooling  the  brine  but  according  to  Mr.  Jos. 
H.  Hart,  the  latter,  making  use  of  direct  expansion,  Is  the 
most  efficient  and  the  one  most  commonly  installed.  The 
loss  by  radiation  to  the  pipes  in  the  conduits  is  not  great  but 
numerous  mechanical  difficulties  are  yet  to  be  overcome.  It 
would  seem  desirable  to  make  the  pipe-line  system  of  cool- 
ing general  for  residence  use  but-  as  yet  it  has  not  been 

found  economical  to  cool  build- 
ings using  less  than  the 
equivalent  of  500  pounds  of  re- 
frigeration in  24  hours.  Al- 
though not  an  efficient  method, 
it  seems  probable  that  cold  air 
refrigeration  by  using  balanced 
expansion  may  supersede  the 
other  systems. 

281.  As  a  Final  Application 
of  refrigeration  we  may  men- 
tion the  cooling  of  the  drinking 
water  supply  in  large  office 
buildings,  hotels,  etc.  Usually 
this  is  simply  a  small  part  of 
the  work  of  a  large  refrigerat- 
ing plant.  Fig.  200  gives  a  dia- 
grammatic elevation  of  such  an 
arrangement. 


Fig.  200. 


CHAPTER  XVII. 


REFRIGERATION    CALCULATIONS 


232.  Unit     Measurement     of     Refrigeration: — Since    the 
first   efforts   toward   refrigeration   employed   the   simple   pro- 
cess of  melting-  ice  by  the  abstraction  of  heat  from  nearby 
articles,    it    is   not   surprising   to   find   the   accepted   standard 
unit  for  expressing  refrigeration   capacities  referred   to   the 
refrigerating    effect   of    a    known    quantity   of    ice.      In    fact, 
since    the    latent   heat    of   fusion    of    ice    is    a    constant,    this 
furnishes    an    excellent    basis    for    estimating    refrigeration. 
The  generally  accepted  unit  of  measure  is  the  ton  of  refrigera- 
tion, which  may  be  defined  as  the  amount  of  heat  (B.  t.  u.)  which 
one  ton  of  2000  pounds  of  ice  at  32  degrees,  will  absorb  in  melting  to 
water  at  32  degrees.     Since  the  latent  heat  of  ice  is  144  B.  t.  u. 
per  pound,  one  ton  of  refrigeration  is  equal  to  288000  B.  t.  u. 
Just   as   a   pumping   plant   is   rated   at  a   certain   number   of 
millions  of  gallons,  meaning  millions  of  gallons   in  twenty- 
four   hours,    so    a    refrigeration    plant    is    rated    in    so    many 
tons  of  refrigeration,  meaning  so  many  tons  in  twenty-four 
hours.     Hence  one  ton  of  refrigeration  capacity  for  one  day 
is  equivalent  to  12000  B.  t.  u.  per  hour,  this  value  being  the 
unit  of  refrigerating  capacity,  sometimes  referred  to  as  tonnage 
capacity,  or  refrigerating  effect,  and  usually  designated  by  T. 

233.  Calculation    of    Required     Capacity: — To     estimate 
closely    the    tonnage    capacity    of    a    refrigerating    plant    for 
any  certain  store  space  requires  specific  attention  to  supply- 
ing the  following  losses: 

(a)  The    radiated    and    conducted    heat    entering    the 
room.     This  may  be  divided  into  that  due  to  the  walls  and 
that  due  to  the  windows  and  sky-lights. 

(b)  The   heat   entering   by   the   renewal   of   the    air,    or 
ventilation  of  the  enclosed  space.     This  may  be  divided  into 
heat    given    off    by    the    air   and    heat    given    off    due    to    the 
latent  heat  of  the  moisture. 

(c)  The  heat  entering  by  the  opening  of  doors. 

(d)  The  heat   from   the   men   at   work,   lights,   chemical 
fermentation  processes,  etc. 

(e)  The  heat  abstracted  from  material  in  cold  storage. 


REFRIGERATION 


379 


Refrigeration  losses  due  to  entrance  of  radiated  and  con- 
ducted Iteat  may  be  calculated  by  Equations  26,  27  and  28, 
Chapter  III,  if  the  proper  transmission  constants  are  in- 
serted. To  obtain  these  constants  for  various  types  of  in- 
sulation use  Tables  VI  and  XL. 


TABLE   XL. 
Heat  Transmission  of  Standard  Types  of  Dry  Insulation. 


Material 

K 

Material 

K 

Mill  shavings,  Type  (a) 
1"  thickness 

1330 

Hair  Felt,  Type  (a) 
1"  thickness 

138 

2"                      _. 

.1090 

W,  W,  W,  Type  (c) 

.105 

3" 

.0920 

Sheet  Cork   Type  (d) 

4" 

0800 

4"  with  1"  air  space 

050 

5"                      

.0710 

5"  with  1"  air  space  

.037 

6" 

0630 

3",  Type  (b) 

087 

7" 

.0570 

1",  Type  (a)      _ 

.137 

8" 

.0520 

Granulated  Cork 

10" 

0440 

4",  Type  (a) 

.071 

12" 

.0390 

Mineral  Wool 

14" 

.0340 

2%",  Type  (b)  _ 

.151 

16" 

.0308 

1",  Type  (b) 

.192 

18"                      

.0279 

Air  Spaces 

20"                        

.0255 

8",  Type  (a)  . 

.112 

22" 

.0235 

24" 

.0218 

TAR  PAPELR- 


In  general  any  space  to  be  kept  at  or  below  zero  degrees 
should  have  insulation  allowing  no  greater  transmission 
than  .04,  and  for  spaces  to  be  kept  at  from  0  degrees  to  30 
degrees  no  greater  transmission  should  be  allowed  than  .06, 
while  for  temperatures  above  30  degrees  a  transmission  as 
great  as  .1  is  allowable.  In  any  case,  however,  it  should  be 


380  HEATING  AND  VENTILATION 

remembered  that  the  heat  loss,  and  therefore  the  expense  of 
operation,  is  directly  proportional  to  this  factor  and  the 
best  possible  insulation,  consistent  with  available  building 
funds,  is  the  one  to  use,  the  ceiling  and  floor  being  as  care- 
fully insulated  as  the  walls.  Window  construction  should 
be  tight,  non-opening,  and  at  least  double. 

The  refrigeration  Joss  due  to  ventilation  may  be  considered 
under  two  heads,  i.  e.,  the  cooling  of  the  air  from  the 
higher  to  the  lower  temperature,  and  the  cooling,  condens- 
ing and  freezing-  of  the  moisture  in  the  air.  In  this  par- 
ticular, air  cooling  cannot  be  considered  exactly  the  re- 
verse of  air  warming.  In  air  warming  the  va.por  present 
absorbs  heat  but  this  vapor  has  so  little  heat  capacity  com- 
pared with  that  of  the  air  that  no  noteworthy  error  is  intro- 
duced by  ignoring  the  vapor.  However,  in  air  cooling  the 
dew  point  is  almost  invariably  reached  and  passed,  so  that 
considerable  moisture  is  changed  from  the  vapor  to  the 
liquid  with  a  liberation  of  its  heat  of  vaporization.  This  is 
considerable  and  cannot  be  ignored  without  serious  error. 
If,  further,  conditions  are  such  that  this  moisture  is  frozen, 
its  latent  heat  of  freezing  must  also  be  accounted  for. 
These  two  items  are  relatively  so  large  that  to  cool  air 
through  a  given  range  of  temperature  may  involve  several 
times  the  heat  transfer  required  to  warm  the  same  air 
through  the  same  range  of  temperature. 

APPLICATION. — Assume  outside  air  95  degrees,  relative 
humidity  85  per  cent.,  temperature  of  air  upon  leaving  cool- 
ing coils  30  degrees  and  temperature  of  coil  surface  10  de- 
grees. If  180000  cubic  feet  of  air  per  hour  are  drawn  in 
from  the  atmosphere,  the  refrigerating  capacity  of  the  coils 
may  be  obtained  as  follows.  To  cool  the  air  from  95  degrees 
to  30  degrees  will  require  (Equation  29), 
180000  X  (95  —  30) 


=   212700  B.  t.  u. 


55 

At  95  degrees  and  85  per  cent,  humidity  one  cubic  foot  of 
air  contains,  (Table  11,  Appendix),  .85  X  17.124  =  14.555 
grains  of  moisture.  At  30  degrees  and  saturation  one  cubic 
foot  of  air  contains,  (Table  11),  1.935  grains.  Hence  there 

180000  (14.555  —  1.935) 

would  be  deposited  upon  the  coils 

7000 

324.5  pounds  of  moisture  per  hour.  Now  there  would  be 
absorbed  from  each  pound  of  this  moisture 


REFRIGERATION  381 

32  B.  t.  u.  to  cool  from  95  to  32  degrees. 

1073  B.  t.  u.  to  change  to  liquid  form. 

144  B.  t.  u.  to  freeze  (if  allowed  to  freeze  on  coils). 

11  B.  t.  u.  to  cool  from  32  to  10  degrees. 

1260   B.  t.  u.  total. 

Hence  the  coils  would  have  to  absorb  from  the  moisture 
alone  1260  X  324.5  =  408870  B.  t.  u.  per  hour,  or  for  both 
moisture  and  air,  212700  +  408870  =  621600  B.  t.  u.  per  hour. 
This  indicates,  for  the  ventilation  proposed,  a  tonnage  capac- 
ity of  621600  -=-  12000  =  51.8  tons  of  refrigeration  needed  at 
the  bunker  room  coils.  The  above-  provides  that  the  air  is 
rejected  at  the  interior  temperature,  30  degrees.  Modern 
plants,  however,  would  pre-cool  the  incoming  air  before  it 
reached  the  bunker  room  by  having  part  of  its  heat  ab- 
sorbed by  the  outgoing  30  degree  air,  which  would  reduce 
the  estimate  somewhat  below  51.8  tons. 

In  considering  the  refrigeration  loss  due  to  the  opening  of 
doors  no  rational  method  of  calculation  is  applicable,  but  if 
the  nature  of  the  cold  storage  service  is  such  that  doors  are 
frequently  opened,  as  high  as  25  per  cent,  may  be  allowed. 
Generally  this  is  taken  from  10  to  15  per  cent. 

The  refrigeration  loss  due  to  persons,  lights,  etc.,  may  be 
estimated  as  suggested  in  Art.  44.  If  the  cooling1  air  is 
recirculated,  the  cooling  and  freezing  of  the  moisture  given 
off  by  each  person  should  be  taken  into  account,  especially 
if  the  number  is  large.  For  this  purpose  it  is  safe  to  assume 
a  maximum  of  500  grains  of  moisture  given  off  per  person 
per  hour  when  such  persons  are  not  engaged  in  active  phy- 
sical exercise. 

234.  Calculations  for  Square  Feet  of  Cooling  Coil: — This 
problem  presents  greater  uncertainty  in  its  solution  than 
does  the  design  of  a  heating  coil  surface  because  of  the  lack 
of  'experimental  data  and  because  of  the  variable  insulat- 
ing effect  of  ice  and  frost  accumulations,  if  allowed  to  form. 
Professor  Hanz  Lorenz  in  "Modern  Refrigerating  Machin- 
ery," page  349,  quotes  4  B.  t.  u.  per  square  foot  per  hour  per 
degree  difference  between  the  average  temperatures  on  the 
inside  and  outside  of  the  coils,  as  a  safe  designing  value 
when  the  air  speed  is  1000  feet  per  minute  over  the  coils. 
This  is  for  plants  in  continuous  operation,  as  abattoirs,  cold 
stores  and  in  places  where  no  provision  is  made  against  ice 


382  HEATING  AND  VENTILATION 

formation.  For  clean  pipe  surface  in  the  plenum  air  cooling 
plant  of  the  New  York  Stock  Exchange  Building  the  heat 
transmission  is  approximately  430  B.  t.  u.  per  square  foot 
per  hour  with  air  over  coils  at  1000  feet  per  minute.  Under 
the  average  temperatures  there  used,  this  corresponds  to  a 
transmission  per  degree  difference  per  square  foot  per  hour 
of  approximately  7  B.  t.  u.  These  two  values,  4  and  7,  may 
be  taken  as  about  the  minimum  and  maximum  transmission 
constants  for  plenum  cooling  coil  installations. 

For  direct  cooling  coils,  where  the  pipe  surface  is  sim- 
_ply  exposed  to  the  air  of  the  room  to  be  cooled,  Lorenz 
recommends  a  transmission  allowance  of  not  over  30  B.  t.  u. 
per  square  foot  per  hour,  for  in  such  installations  the  re- 
moval of  ice  and  frost  is  seldom  contemplated.  For  an  aver- 
age room  temperature  of  30  degrees  and  average  brine  tem- 
perature of  10  degrees,  this  would  correspond  to  30  -4-  20  = 
1.5  B.  t.  u.  transmitted  per  square  foot  per  hour  per  degree 
difference. 

APPLICATION  1.  —  How  many  lineal  feet  of  1*4  inch  direct 
refrigerating  coils  would  be  required  to  keep  a  cold  stor- 
age room  at  30  degrees  if  the  refrigeration  loss  is  80000 
B.  t.  u.  per  hour  total  and  the  temperatures  of  the  brine  en- 
tering and  leaving  the  coils  are  10  degrees  and  20  degrees 
respectively?  Average  brine  temperature  =  15  degrees.  Al- 
lowing a  transmission  constant  of  1.5,  Equation  51  becomes, 
H 


=  —  .0445  // 


1.5  (15  —  30) 

For  this  problem  we  have  .0445   X   80000  =  3500  square  feet, 
or  3500   X   2.3  =  8050  lineal  feet  of  1%  inch  pipe. 

APPLICATION  2. — The  cooling  of  180000  cubic  feet  of  air  per 
hour  in  Art.  233  required  the  extraction  of  621600  B.  t.  u.  per 
hour.  Determine  the  plenum  cooling  surface  required,  if 
brine  enters  at  0  degrees  and  leaves  at  20  degrees. 

Average  brine  temperature  =  10  degrees.  Assuming- 
that  there  is  provision  for  keeping  coils  clear  of  ice,  and 
hence  a  transmission  constant  of  7  B.  t.  u.  is  allowable, 
Equation  65  gives 

621600 
Rr  =  —  =  —  1691  square  feet  of  surface. 

95  +  30 


( 
10  - 


REFRIGERATION  383 

The  negative  sign  indicates  a  flow  of  heat  in  the  direc- 
tion opposite  to  the  flow  in  heating-  installations,  for  which 
the  equation  was  primarily  designed. 

235.  General  Application: — Considering  the  school  build- 
ing and  the  table  of  calculated  results  as  given  in  Art.  155, 
what  amount  of  cooling  coil  surface  would  be  required  to 
keep  the  temperature  of  all  rooms  of  this  building  at  73 
degrees  on  a  day  when  the  outside  air  temperature  is  95 
degrees  and  the  relative  humidity  85  per  cent.? 

Data  Table  XXXV  gives  the  total  heat  loss  of  the  three 
floors  of  this  building  as  1483250  B.  t.  u.  per  hour  on  a  zero 
day  when  the  rooms  are  kept  at  70  degrees.  Now  this  same 
building  under  the  summer  conditions  would  have  delivered 
to  it  heat  due  to  a  temperature  difference  of  95  degrees  —  73 
degrees  =  22  degrees.  Hence  the  total  refrigeration  loss  dur- 

22 

ing  the  summer  day  would  be  approximately X  1483250  = 

70 

466000  B.  t.  u.  per  hour,  which  amount  of  heat  would  be  used 
to  warm  the  incoming  air  from  some  temperature  up  to  73 
degrees.  Suppose  the  ventilation  requirement  of  the  build- 
ing is  2000000  cubic  feet  per  hour.  Since  it  requires  1/56  of 
a  B.  t.  u.  to  warm  one  cubic  foot  of  air  one  degree,  [2000000 
(73  —  *)]  -j-  55  =  466000,  or  *  =  60.2,  say  60  degrees.  (See 
Arts.  50  and  51  and  observe  that  the  second  term  of  the  right 
hand  member  of  Equation  36  becomes  a  negative  term). 

While  the  air  is  traversing  the  ducts  between  the  coils 
and  the  rooms,  allow  a  rise  in  temperature  of  5  degrees. 
The  coils  would  then  be  required  to  deliver  2000000  cubic 
feet  of  air  per  hour  at  55  degrees  when  supplied  with  air  at 
90  degrees  and  85  per  cent,  humidity.  To  cool  this  amount 
of  air  through  the  given  range  would  require  the  absorption 
of  (Equation  29)  [2000000  X  (95  —  55)]  -r-  55  -  1454500  B.  t.  u. 
At  95  degrees  and  85  per  cent,  humidity,  I  cubic  foot  of  air 
contains  (Table  11),  .85  X  17.124  =  14.555  grains  of  moisture. 
At  55  degrees  and  saturation  point,  1  cubic  foot  of  air  con- 
tains (Table  11),  4.849  grains  of  moisture.  Hence,  neglecting 
change  in  air  volume,  there  would  be  deposited  on  the  coils 
approximately  [2000000  (14.555  --  4.849)]  4-  7000  =  2775 
pounds  of  moisture  per  hour. 

Now,  if  an  average  brine  temperature  of  10  degrees  is 
used  and  provision  is  made  for  keeping  the  coils  clear  of  ice, 
the  condensation  will  leave  at  some  temperature  above  10 


384  HEATING  AND   VENTILATION 

degrees,  say  20  degrees,  and  there  will  be  absorbed  from 
each  pound  of  this  moisture  approximately 

20  B.  t.  p.  to  cool  from  95  to  55  degrees. 
1061  B.  t.  p.  to  change  to  liquid  form  at  55  degrees. 

35   B.  t.  u.  to  cool  the  water  from  55  to  20  degrees. 

1116   B.  t.  u.  total. 

Hence  the  coils  would  have  to  absorb  from  moisture  alone, 
2775  X  1116  =  3096900  B.  t.  u.,  or  from  both  moisture  and  air 
a  total  of  1454500  +  3^)96900  =  4551400  B.  t.  u.  per  hour.  At 
an  allowed  rate  of  transmission  of  7  B.  t.  u.  there  would  be 
required  to  cool  this  building  a  total  of  approximately  9100 
square  feet  of  coil  surface,  under  the  conditions  of  ventila- 
tion as  assumed. 

It  should  be  noted  that  whereas  less  than  3000  square  feet 
of  plenum  surface  were  sufficient  to  heat  the  building  ac- 
cording to  Application  2,  Art.  137,  it  requires  fully  three 
times  this  amount  of  surface  in  cooling  coils  to  cool  the 
building  under  the  assumed  conditions.  Upon  inspection  it 
is  seen  that  the  greatest  work  of  the  cooling  coils  is  the 
condensation  and  cooling  of  the  moisture. 

The  relative  humidity  within  the  cooled  rooms  would  be 
approximately  55  per  cent.,  for  the  content  per  cubic  foot  of 
incoming  air  is  4.849  grains,  and  the  capacity  of  the  air 
when  heated  to  73  degrees  is  8.782  grains  showing  a  relative 

4.849 

humidity,  after  heating,  of =  55  per  cent.     This  would 

8.782 

be  raised  somewhat  by  the  persons  present. 

236.  Ice  Making  Capacity.  Calculation: — Neglecting 
losses,  the  ice  making  capacity  of  a  refrigerating  plant  for 
a  certain  refrigeration  tonnage  may  be  expressed 

144   T 

I  = (132) 

(t  —  32)  +  144  +  .5  (32  —  *i) 

in  which  /  =  tons  of  ice  produced  per  24  hours,  T  =;  refrig- 
eration tonnage  or  rating  of  plant,  t  =  initial  temperature  of 
water  and  t^  =  final  temperature  of  ice,  usually  12  to  18 
degrees. 

APPLICATION. — What  should  be  the  ice  making  capacity  of 
a  plant  having  a  tonnage  rating  of  100,  if  t  =  70  degrees  and 
ti  =  16  degrees?  Take  losses  at  35  per  cent. 

.65  X  144  X  100 

/  = =  49.3  tons  in  24  hours. 

(70  —  32)  +  144  +  .5  (32  —  16) 


REFRIGERATION  385 

237.  Gallon  Degree  Calculation:  —  For  use  in  plants  pro- 
ducing ice  by  brine  circulation  a  unit  called  the  gallon  degree 
is  sometimes  used.  It  represents  a  change  of  one  degree 
temperature  in  1  gallon  of  brine  in  one  minute  of  time.  It 
is  not  a  fixed  unit  representing  a  constant  number  of 
B.  t.  u.,  since  the  brine  strength,  and  therefore  its  specific 
heat,  may  vary.  The  value  in  B.  t.  u.  per  minute,  of  a  gallon 
degree  for  any  plant  may  be  obtained  by  multiplying  the 
specific  gravity  of  the  brine  by  its  specific  heat  and  by  8.35, 
the  weight  of  one  gallon  of  water,  or  as  an  equation  may  be 
stated 

D  =   8.35  gh  (133) 

where  D    =   B.  t.  u.   per  minute  equal   to  one  gallon  degree, 
g  —   specific  gravity  of  brine  and  h  =   specific  heat  of  brine. 

The  number  of  gallon  degrees  per  ton  of  refrigerating  capacity 
may  be  found  by  dividing  200  by  D,  since  one  ton  of  refrig- 
erating capacity  is  equal  to  200  B.  t.  u.  per  minute,  then 

200  24 

Dt   —  —  —  for  all  practical  purposes.       (134) 

8.35  gh  gh 

The  refrigerating  capacity  of  a  given  brine  circulation  may  be 
obtained  by  dividing  the  product  of  the  gallons  circulated 
and  the  rise  in  brine  temperature  by  the  value  Dt.  Stated 
as  an  equation  this  is 


T  =  -  (135) 

Dt  24 

where   T    =    tonnage   capacity,   O   =    gallons   of   brine   circu- 

lated per  minute  and   (t2  —  ts)    =   rise  of  brine  temperature. 

23S.      Refrigerating    Capacity   of  Brine   Cooled   System:  — 

To  calculate  the  capacity  but  two  things  are  required,  the 
amount  of  brine  circulated,  and  the  rise  in  temperature  of 
the  brine.  From  these  the  capacity  may  be  obtained  by 
the  equation 

Wh  (t-2  —  *a) 

T  =  --  •  (136) 

12000 

where  T  ~  tonnage  capacity,  W  =  weight  of  brine  circulated, 
in  pounds,  h  =  specific  heat  of  brine  and  (t2  —  t3)  =  rise  in 
temperature  of  brine. 

239.  Cost  of  Ice  Making  and  Refrigeration:  —  The  cost  of 
ice  manufacture  is  affected  principally  by  the  following 
items:  price  and  kind  of  fuel,  kind  of  water,  cost  of  labor, 
regularity  of  operation,  method  of  estimating  costs,  etc. 


386  HEATING  AND  VENTILATION 

It  is  found  in  practice  to  range  anywhere  from  $0.50  to 
$2.50  per  ton.  The  items  making-  up  the  cost  of  ice  manu- 
facture are:  fuel  for  power,  labor  at  the  plant,  water,  am- 
monia and  minor  supplies,  maintenance  of  the  plant,  inter- 
est and  taxes,  and  administration.  Mr.  J.  E.  Siebel  in  his 
"Compend  of  Mechanical  Refrigeration  and  Engineering" 
gives  an  itemized  account  of  the  daily  operating  expense  of 
a  100-ton  plant  with  which  he  was  connected,  the  plant 
operating  24  hours  per  day. 

Chief  engineer  $     5.00 

Assistant  engineers  6.00 

Firemen    4.00 

Helpers  5.00 

Ice  pullers  9.00 

Expenses    12.00 

Coal  at  $1.10  per  ton  18.00 

Delivery  (wholesale)  50c  per  ton 50.00 

Repairs,  etc 3.00 

Insurance,  taxes,  etc 6.00 

Interest  on  capital  '. 20.55 

Total  for  100  tons  of  ice $138.55 

The  length  of  time  that  the  ice  is  permitted  to  freeze 
is  a  factor  affecting  the  cost  of  production.  The  following 
figures  are  given  for  a  10-ton  plant: 

Ten  tons  Ten  tons 

in   12   hours  in   24  hours 

.Engineer  $2.50  $5.00 

Fireman    1.50  3.00 

Tankmen,  helpers ....  1.50  3.00 

Coal     3.00  3.00 

Repairs,  supplies,  etc.  1.50  1.50 


Total  for  10  tons       $10.00  $15.50 

Mr.  A.  P.  Criswell,  in  "Ice  and  Refrigeration,"  gives  the 
following  approximate  costs  for  the  production  of  can  ice 
per  ton  with  coal  at  $2.50  per  ton  and  with  a  simple  distill- 
ing system.  The  figures  are  for  the  plant  operating  at  full 
capacity  and  do  not  include  cost  of  administration. 


REFRIGERATION  387 

Capacity  of  plant  Cost  per  ton 

10  tons   $1.58 

20      "        1.48 

30      " 1.42 

40      "        1.38 

50      " 1.36 

70      "         1.34 

100      "        1.34 

120      "        1.30 

Mr.  Karl  Wegemann  states  that  a  certain  moderate  sized 
plant  of  the  absorption  system  produced  ice  for  a  number 
of  years  at  an  average  cost  of  $0.85  per  ton  after  allowing 
for  melting  and  breakage.  This  included  all  charges  ex- 
cept for  interest,  insurance  and  administration. 

The  following  figures  taken  from  the  books  of  another 
plant  show  clearly  the  effect  of  demand  upon  the  cost  of 
manufacture. 

Month  Cost  per  ton 

January    $3.50 

February    3.70 

March    2.80 

April    2.17 

May    1.75 

June  1.19 

July   1.02 

August    1.02 

September 1.03 

October 1.26 

November  2.10 

December  ...  2.94 


CHAPTER  XVIII. 


PLANS    AND    SPECIFICATIONS    FOR    HEATING    SYSTEMS. 

In   Planning   for   and    Executing   Engineering   Contract*, 

the  responsibilities  assumed  by  the  various  interested  parties 
should  be  thoroughly  studied.  The  following  outline  shows 
the  relationship  between  these  parties  and  the  order  of  the 
responsibility. 


/Engineer. 

J  Superintendent  and  Inspector. 

\General  contractor,  Subcontractors,  Foremen  and 
Purchaser  I 

Workmen. 


The  engineer,  the  superintendent  and  the  general  con- 
tractor occupy  positions  of  like  responsibility  with  relation 
to  the  purchaser.  The  first  two  work  for  the  interest  of  the 
purchaser  to  obtain  the  best  possible  results  for  the  least 
money,  and  the  last  endeavors  to  fulfill  the  contract  to  the 
satisfaction  of  the  superintendent,  at  the  least  possible  ex- 
pense to  himself.  These  points  of  view  are  quite  different 
and  sometimes  are  antagonistic,  but  both  are  right  and  just. 
Of  the  three  parties,  the  engineer  has  the  greatest  respon- 
sibility. It  is  his  duty  to  draw  up  the  plans  and  to  write 
the  specifications  in  such  a  way  that  every  point  is  made 
clear  and  that  no  question  of  dispute  may  arise  between  the 
superintendent  and  the  contractor.  His  plans  should  detail 
every  part  of  the  design  with  full  notes.  His  specifications 
should  explain  all  points  that  are  difficult  to  delineate  on  the 
plans.  They  should  give  the  purchaser's  views  covering  all 
preferences,  and  should  definitely  state  where  and  what  ma- 
terials may  be  substituted.  Where  any  point  is  not  definitely 
settled  and  left  to  the  judgment  of  the  contractor,  he  may 
be  expected  to  interpret  this  point  in  his  favor  and  use  the 
cheapest  material  that  in  his  judgment  will  give  good  re- 
sults. This  opinion  may  differ  from  that  held  by  the  pur- 
chaser. All  parts  should  be  made  so  plain  that  no  two  opin- 
ions could  be  had  on  any  important  point.  The  engineer 


TYPICAL,   SPECIFICATIONS  389 

should  also  be  careful  that  the  plans  and  specifications  agree 
in  every  part.  The  inspector  is  the  superintendent's  repre- 
sentative on  the  grounds  and  is  supposed  to  inspect  and 
pass  upon  all  materials  delivered  on  the  grounds,  and  the 
quality  of  workmanship  in  installing.  For  such  information 
see  Byrne's  "Inspector's  Pocket-Book."  The  general  con- 
tractor usually  sublets  parts  of  the  contract  to  subcon- 
tractors who  work  through  the  foreman  and  workmen  to 
finish  the  work  upon  the  same  basis  as  the  general  con- 
tractor. 

The  following  brief  set  of  specifications  are  not  con- 
sidered complete  but  are  merely  inserted  to  suggest  how 
such  work  is  done. 

Typical   Specifications. 
TITLE  PAGE  : — 

SPECIFICATIONS 

for  the 

MATERIALS  AND  WORKMANSHIP 
Required  to  Install 


(Type  of  system) 

HEATING   AND  VENTILATING   SYSTEM 
in  the 


(Building) 


(Location) 
by 


(Name  of  designer) 
INDEX  PAGE  : — 

(To  be  compiled  after  the  specifications  are  written.) 

General  Remarks  to  Contractor. — In  the  following  specifica- 
tions,  all   references   to   the  Owner   or   Purchaser   will   mean 

-or  any  person  or  persons  delegated  by 

to  serve  as  the  representative.  The  Super- 
intendent of  Buildings  will  be  the  purchaser's  representative  at 
all  times,  unless  otherwise  definitely  stated.  The  contractor 
will,  therefore,  refer  all  doubtful  questions  or  misunder- 
standings, if  any,  to  the  superintendent  whose  decision  will 
be  final.  In  case  of  any  doubt  concerning  the  meaning  of 


390  HEATING  AND  VENTILATION 

any  part  of  the  plans  or  specifications,  the  contractor  shall 
obtain  definite  interpretation  from  the  superintendent  be- 
fore proceeding-  with  the  work. 

These  specifications  with  the  accompanying-  plans  and 

details  (sheets  to  inclusive)  cover  the  purchase  of 

all  the  materials  as  specified  later  (the  same  materials  to 
be  new  in  every  case),  and  the  installation  of  the  same  in  a 
first  class  manner  within  the  above  named  building-,  located 
at  (street)  (city)  (state). 

It  will  be  understood  that  the  successful  bidder,  herein- 
after called  the  contractor,  shall  work  in  conformity  with 
these  plans  and  specifications  and  shall,  to  the  best  of  his 
ability,  carry  out  their  true  intent  and  meaning-.  He  shall 
purchase  and  erect  all  materials  and  apparatus  required  to 
make  the  above  system  complete  in  all  its  parts,  supplying 
only  such  quality  of  materials  and  workmanship  as  will  har- 
monize with  a  first  class  system  and  develop  satisfactory 
results  when  working-  under  the  heaviest  service  to  which 
such  plants  are  subjected. 

The  contractor  shall  lay  out  his  own  work  and  be  re- 
sponsible for  its  fitting  to  place.  He  shall  keep  a  competent 
foreman  on  the  grounds  and  shall  properly  protect  his  work 
at  all  times,  making-  g-ood  any  damage  that  may  come  to  it, 
or  to  the  building-,  or  to  the  work  of  other  contractors  from 
any  source  whatsoever,  which  may  be  chargeable  to  himself 
or  to  his  employees  in  the  course  of  their  operations. 

Any  defects  in  materials  or  workmanship,  other  than 
as  stated  under — (state  exceptions  if  any) — that  may  develop 
within  one  year,  shall  be  made  good  by  the  contractor  upon 
written  notification  from  the  purchaser  without  additional 
cost  to  the  purchaser. 

The  contractor  shall,  wherever  it  is  found  necessary, 
make  all  excavations  and  back-fill  to  the  satisfaction  of  the 
superintendent. 

The  contractor  shall  be  responsible  for  all  cuttings  of 
wood  work,  brick  work  or  cement  work,  found  necessary 
In  fitting-  his  materials  to  place,  either  within  or  without  the 
building-;  the  cutting-  to  be  done  to  the  satisfaction  of  the 
superintendent.  The  contractor  shall  be  required  to  connect 
and  supply  water  and  gas  for  building  purposes,  and  shall 
assume  all  responsibility  for  the  same. 


TYPICAL   SPECIFICATIONS  391 

The  contractor  shall  be  required  to  protect  the  purchaser 
from  damage  suits,  originating  from  personal  injuries  re- 
ceived during  the  progress  of  the  work;  also,  from  actions 
at  law  because  of  the  use  of  patented  articles  furnished  by 
the  contractor;  also,  from  any  lien  or  liens  arising  because 
of  any  materials  or  labor  furnished. 

The  purchaser  reserves  the  right  to  reject  any  or  all 
bids. 

No  changes  in  these  plans  and  specifications  will  be 
allowed  except  upon  written  agreement  signed  by  both  the 
contractor  and  the  purchaser's  representative. 

System. — Specify  the  system  of  heating-  in  a  general  way; 
high  pressure,  low  pressure  or  vacuum;  direct,  direct-indi- 
rect or  indirect  radiation;  basement  or  attic  mains;  one-  or 
two-pipe  connections  to  radiators.  If  ventilation  is  provided, 
state  the  movement  of  the  air  and  the  general  arrangement 
of  fans,  coils  or  other  heating  surfaces.  Single  or  double 
duct  air  lines,  etc. 

Boilers. — Specify  type,  number,  size  and  capacity,  steam 
pressure,  approximate  horse-power,  heating"  surface,  grate 
surface  and  kind  of  coal  to  be  used.  Locate  on  plan  and  ele- 
vation. Explain  method  of  setting,  portable  or  brick. 
Specify  also,  flue  connection,  heating  and  water  pipe  connec- 
tions, kind  of  grate,  thermometers,  gages,  automatic  damper 
connection,  firing  tools  and  conditions  of  final  tests. 

Conduits  and  Conduit  Mains. —  (In  this  it  is  assumed  that  the 
boilers  are  not  within  the  building).  In  addition  to  the  lay- 
out, give  sections  of  the  conduit  on  plans  showing  method 
of  construction,  supporting  and  insulating  pipes,  and  drain- 
age of  pipes  and  conduits.  Specify  quality  and  size  of  mate- 
rials, pitch  and  drainage  of  pipes  and  all  other  points  not 
specially  provided  for  in  the  plans. 

Anchors. — Locate  and  draw  on  plans  and  specify  for  the 
installation  regarding  quality  of  materials. 

Expansion  Joints  or  Take-ups. — Locate  and  draw  on  plans. 
Select  type  of  joint  and  specify  for  amount  of  safe  take-up 
and  for  quality  of  material. 

Mains  and  Returns. — Trace  the  steam  from  the  point  where 
it  enters  the  main,  through  all  the  special  fittings  of  the 

system.     Show  where  the  condensation  is  dripped 

to  the  returns  through  traps  or  separating  devices.     Specify 
amount  and  direction   of  pitch,   kind   of  fittings    (flanged   or 


392  HEATING  AND  VENTILATION 

screwed,  cast  iron  or  malleable  iron),  kind  of  corners  (long 
or  short),  method  of  taking  up  expansion  and  contraction. 
Trace  returns  and  specify  dry  or  wet. 

Branches  to  Risers. — Take  branches  from  top  of  mains  by 
tees,  short  nipples  and  ells,  and  enter  the  bottom  of  the 
risers  by  sufficient  inclination  to  give  good  drainage. 

Risers. — Locate  risers  according  to  plan.  They  shall  be 
straight  and  plumb  and  shall  conform  to  the  sizes  given  on 
the  plans.  No  riser  shall  overlap  the  casing  around  win- 
dows. State  how  branches  are  to  be  taken  off  leading  to 
radiators,  relative  to  the  ceiling  or  floor. 

Radiator  Connections. — Specify,  one-pipe  or  two-pipe,  num- 
ber and  kind  of  valves,  sizes  of  connections  and  hand  or 
automatic  control.  All  connections  shall  allow  for  good 
drainage  and  expansion.  Distinguish  between  wall  radiator 
and  floor  radiator  connections.  If  automatic  control  is  used, 
hand  valves  at  the  radiators  are  usually  omitted. 

Radiators. — Specify  floor  or  wall  radiators,  with  type, 
height,  number  of  columns  and  number  of  sections.  If  other 
radiators  are  substituted  for  the  ones  that  are  referred  to 
as  acceptable,  they  must  be  of  equal  amount  of  surface  and 
acceptable  to  the  superintendent.  Specify  brackets  for  wall 
radiators,  also,  air  valves  for  all  radiators,  stating  type 
and  location  on  the  radiator.  Require  all  radiators  to  be 
cleaned  with  water  or  steam  at  the  factory  and  plugged  at 
inlet  and  outlet  for  shipment. 

Piping. — Define  quality,  weight  and  material  in  all  mains, 
branches  and  risers.  All  sizes  above  one  and  one-half  inch 
are  usually  lap  welded.  Piping  should  be  stood  on  end  and 
pounded  to  remove  all  scale  before  going  into  the  system. 
All  pipes  1  inch  and  smaller  should  be  reamed  out  full  size 
after  cutting. 

Fittings. — Specify  quality  of  fittings,  whether  light,  stand- 
ard or  heavy,  malleable  or  cast  iron.  Fittings  with  imper- 
fect threads  should  be  rejected. 

Valves. — Specify  type  (globe,  gate  or  check),  whether 
flanged  or  screwed,  rough  or  smooth  body,  cast  iron  or 
brass,  and  give  pressure  to  be  carried.  All  valves  should 
be  located  on  the  plans. 

Expansion  Tank. — Specify  capacity  of  tank  in  gallons,  kind 
of  tank  (square  or  round,  wood  or  steel),  method  of  connect- 
ing up  with  fittings  and  valves,  and  locate  definitely  on  plan 


TYPICAL   SPECIFICATIONS  393 

and  elevation.  Connect  also  to  fresh  water  supply  and  to 
overflow. 

Hangers  and  Ceiling  Plates. — Wall  radiators  and  horizontal 
runs  of  pipe  shall  be  supported  on  suitable  expansion  hang- 
ers or  wall  supports  that  will  permit  of  absolute  freedom  of 

expansion.  Supports  shall  be  placed  feet  centers.  Pipe 

holes  in  concrete  floors  shall  be  thimbled.  Holes  through 
wooden  walls  and  floors  shall  have  suitable  air  space  around 
the  pipe,  and  all  openings  shall  be  covered  with  ornamental 
floor,  ceiling-  or  wall  plates. 

Traps. — Specify  type,  size,  capacity. and  location.  State 
whether  flanged  or  screwed  fittings  are  used  and  whether 
by-pass  connection  will  be  put  in.  Refeu  to  plans. 

Pressure  Regulating  Valve. — Specify  type,  size  and  location, 
also  maximum  and  minimum  steam  pressure,  with  guaran- 
tee to  operate  under  slight  change  of  pressure.  State  if 
by-pass  should  be  used  and  explain  with  plans. 

Separators. — Specify  type  (horizontal  or  vertical),  also 
size  and  location. 

Automatic  Control. — The  contractor  will  be  held  responsible 
for  the  installation  of  all  thermostats,  regulator  valves,  air 
compressor,  piping  and  fittings  required  to  equip  all  rooms 
and  halls  with  an  automatic  temperature  control  sys- 
tem. Specify  approximate  location  and  number  of  thermo- 
stats with  the  desired  finish.  Specify  in  a  general  way,  reg- 
ulator valves  on  radiators,  quality  of  pipe,  maximum  test 
pressure  for  pipe,  power  for  air  supply  (hydraulic,  pneu- 
matic, etc.),  and  supply  tank.  All  materials  in  the  tem- 
perature control  system  shall  be  guaranteed  first  class  by 
the  manufacturer  through  the  contractor,  and  the  system 
shall  be  guaranteed  to  give  perfect  control  for  a  period  of 
(two)  years. 

Fans. — Specify  for  direct  connected  or  belt  driven,  right 
or  left  hand,  capacity,  size,  housing,  direction  of  discharge, 
horse-power,  R.  P.  M.  and  pressure.  State  in  a  general  way 
the  requirements  of  the  fan  wheel,  steel  plate  housing,  shaft, 
bearings  and  the  method  of  lubrication. 

Engine. — Specify  type,  horse-power,  steam  pressure,  ap- 
proximate cut-off,  speed  and  kind  of  control. 

Electric  Motors. — Specify  type,  horse-power,  voltage,  cycles, 
phases  and  R.  P.  M. 


394  HEATING  AND  VENTILATION 

Indirect  Heating  Surface. — Specify  the  kind  of  surface  to 
be  put  in  and  then  state  the  total  number  of  square  feet 
of  surface,  with  the  width,  height  and  depth  of  the  heater. 
State  definitely  how  the  heaters  will  be  assembled,  giving 
free  height  of  heater  above  the  floor.  Describe  damper  con- 
trol, steam  piping  to  and  from  heater,  housing  around  heater, 
connection  from  cold  air  inlet  to  heater  and  connection  from 
heater  to  fan.  See  plans.  The  contractor  will  usually  follow 
installation  instructions  given  by  the  manufacturers  for  the 
erection  of  the  heater  and  engine,  consequently  the  specifi- 
cations should  bear  heavily  only  upon  those  points  which 
may  be  varied  to  suit  any  condition.  All  valves,  piping  and 
fittings  in  this  work  should  be  controlled  by  the  general 
specifications  referring  to  these  parts. 

Foundations. — Specify  materials  and  sizes. 

Air  Ducts,  Stacks  and  Galvanised  Iron  Work. — The  drawings 
should  give  the  layout  of  all  the  air  lines,  giving  connections 
between  the  air  lines  and  the  fan,  and  the  air  lines  and  the 
registers.  Where  these  air  lines  are  below  the  floor,  the 
conduit  construction  should  be  carefully  noted.  All  gal- 
vanized iron  work  should  be  shown  on  the  plans  and  the 
quality  and  weight  should  be  specified.  Air  lines  should 
have  long  radius  turns  at  the  corners. 

Registers. — Specify  height  above  floor,  nominal  size  of 
register,  method  of  fitting  in  wall,  the  finish  of  the  regis- 
ter and  whether  fitted  with  shutters  or  not. 

Protection  and  Covering. — Specify  kind  and  quality  of  pipe 
covering  and  the  finish  of  the  surface  of  the  covering.  State 
the  amount  of  space  between  heating  pipes  and  unprotected 
woodwork.  Distinguish  between  pipes  that  are  to  be  covered 
and  those  that  are  to  be  painted.  All  radiators  and  piping 

not  covered  should  be  painted  with  two  coats  of  bronze 

or  other  finish  acceptable  to  the  superintendent. 

Completion. — Require  all  rubbish  removed  from  the  build- 
ing and  immediate  grounds  and  deposited  at  a  definite  place. 


SUGGESTIONS    TO    SCHOOL    DISTRICTS. 


It  frequently  happens  that  School  Boards  and  School 
Trustees  are  required  to  select  from  a  number  of  proposed 
heating  and  ventilating-  systems  that  one  which  is  best 
suited  to  their  needs.  Public  officials,  as  a  rule,  are  not  ex- 
pected to  be»engineers  and  occasionally  make  a  selection 
which  afterward  proves  to  be  a  misfit.  The  following-  sug- 
gestions, therefore,  are  offered  in  the  hope  that  some  men 
may  be  benefited  thereby. 

DEFINITIONS. 

Radiating  surfaces. — Radiators,  coils  and  stoves. 

Circulating  air. — Air  which  passes  over  the  radiating1 
surfaces  and  carries  heat  to  the  rooms.  This  may  be  outside 
air  or  returned  air  from  the  rooms. 

Ventilating  air. — Circulating-  air  taken  from  without  the 
building. 

Direct  system. — Radiating-  surfaces  set  within  the  rooms 
to  be  heated.  No  special  outside  air  connections. 

Indirect  system. — Radiating  surfaces  set  in  the  basement 
or  somewhere  within  the  building  and  below  the  rooms  to  be 
heated.  Air  is  passed  over  these  radiating-  surfaces,  heated 
and  carried  through  ducts  to  the  rooms.  When  this  air  is 
taken  from  without  the  building  there  is  provision  for  good 
ventilation. 

Direct-indirect  system. — Radiating1  surfaces  set  within 
the  rooms  to  be  heated,  usually  next  the  outside  wall,  ajid 
supplying1  ventilating-  air  for  the  rooms  by  means  of  short 
ducts  through  the  walls.  A  fair  quality  of  ventilation  may 
be  obtained  under  favorable  conditions. 

One-pipe  steam  system. — Radiators  connected  at  one  bot- 
tom end  only.  This  serves  both  for  steam  inlet  and  con- 
densation return.  Air  valves  are  a  necessity  and  are  located 
about  mid-height  on  the  last  coil  of  the  radiator. 

Two-pipe  steam  system. — Radiators  double  connected; 
bottom  for  return,  and  top  or  bottom  for  steam.  Where  top- 
connected  for  steam,  use  water-type  radiator  only.  Air 
valves  useful  but  not  as  necessary  as  on  one-pipe  system. 

Low-pressure  steam  system. — Steam  circulated  by  grav- 
ity at  pressures  between  0  and  5  pounds  gage. 

Atmospheric  and  vapor  systems. — Steam  circulated  by 
gravity  at  0  to  0-pressures.  Radiators  always  two-pipe, 
water-type,  top-connected  for  steam.  '  Graduated  inlet  valve. 
Air  valves  on  end  of  return. 

Mechanical  vacuum  systems. — Steam  pressures  0  to  5 
pounds  gage.  Condensation  returned  by  pump  below  atmos- 


396  HEATING  AND  VENTILATION 

pheric  pressure.  Circulation  positive.  Returns  smaller  than 
gravity  returns.  Air  valve  on  return  tank. 

Gravity  room-heater  system.  —  Large  metal-encased 
stoves  set  within  the  rooms  to  be  heated  and  circulating 
room  air  or  outside  air  upward  between  the  stove  and  cas- 
ing, thus  heating-  it  for  room  use.  When  the  afr  is  partially 
or  wholly  taken  from  the  outside  of  the  building,  this  heater 
makes  a  direct-indirect  system. 

Aspirating  vent  flues. — Smooth  vertical  flues  containing 
heating  coils  and  leading  to  the  outside  air  through  the 
roof.  These  flues  should  be  located  in  the  partition  walls 
of  the  building.  The  heating  coils  create  ascending  cur- 
rents of  air  within  the  flues  and  assist  room  ventilation. 

Cowls. — Metal  cappings  on  the  tops  of  the  ventilating 
flues,  so  constructed  as  to  assist  convection  currents  within 
the  flues  and  prevent  down  drafts. 

Gravity  warm-air  furnace  system. — A  large  metal-  or 
brick-encased  stove,  usually  set  in  the  basement,  and  having 
one  or  more  circulating  air  pipes  leading  into  and  from  the 
space  between  the  stove  and  the  casing.  Circulation  is  main- 
tained wholly  by  the  difference  in  weight  (density)  between 
the  warmer  air  at  the  furnace  and  that  of  the  cooler  sur- 
rounding atmosphere.  The  entire  circulating  air  may  be  re- 
turned from  the  rooms  to  the  furnace,  in  which  case  there 
is  no  ventilating  effect;  or,  a  part  of  the  air  may  be  recir- 
culated  with  part  taken  from  the  outside,  giving  some  ven- 
tilating effect;  or,  all  the  air  may  be  taken  from  the  out- 
side, with  the  best  ventilating  effect.  All  furnace  systems 
should  have  outside  air  connections  of  such  size  as  will  per- 
mit all  the  air  to  be  taken  from  the  outside. 

Fan-furnace  systems. — A  hot  air  furnace,  similar  in  prin- 
ciple to  the  gravity  warm-air  furnace,  with  blower  attach- 
ment. Circulating  air  temperatures  generally  higher  than 
those  of  the  warm-air  furnace  system. 

Fan-coil  system. — Metal-encased  steam-coils  as  heating 
surfaces,  with  air  circulation  over  the  coils  maintained  by 
blower  attachment.  Best  ventilating  possibilities.  Circulat- 
ing air  temperatures  about  the  same  as  in  the  gravity  warm- 
air  furnace  system. 

Ventilating  systems. — These  may  be  either  independent 
of  or  a  part  of  the  heating  system.  The  air  supply  for  ven- 
tilation shall  be  from  an  uncontaminated  source,  or  shall  be 
air  from  which  the  dust  or  other  impurities  shall  be  removed 
by  efficient  air  cleansing  devices.  Circulation  may  be  pro- 
duced by  gravity,  in  which  case  the  air  movement  is  slug- 


SUGGESTIONS  TO   SCHOOL  DISTRICTS  397 

gish  and  the  ducts  and  stacks  necessarily  large;  or  by 
mechanical  means,  resulting-  in  higher  air  velocities  and 
correspondingly  smaller  ducts  and  stacks.  Positive  air  cir- 
culation in  vent  stacks  is  very  important  in  all  gravity  air 
circulating  plants.  Where  electric  power  is  available,  me- 
chanical circulation  by  fans  is  the  most  satisfactory  and  is 
the  least  expensive  system  to  operate.  Where  power  is  not 
available,  circulation  may  be  obtained  by  the  use  of  aspirat- 
ing coils  and  cowls.  Although  aspiration  is  a  wasteful  pro- 
cess, it  is  practically  fool-proof.  In  large  plants  where  the 
exhaust  steam  may  be  used  in  coils  for  .heating,  steam  en- 
gine-driven fans  for  the  air  supply  are  more  economical  than 
electric  drives.  Gas  engine  drives  are  noisy  and  unreliable 
and  should  be  used  in  school  systems  only  as  a  last  resort. 

CLASSIFICATION    OP    SYSTEMS. 

The    following   classification   is    suggestive   only,    and    is 
intended   as  an   aid   to   show  those   systems  best  adapted   to 
the  different  types  of  school  buildings. 
One-room  building,  110  basement. 

Direct-indirect  room-heater. 
One-room  building:,  with  basement. 

Gravity  furnace  system. 

Indirect,  one-pipe  or  two-pipe  steam  system. 

Direct-indirect,  one-pipe  or  two-pipe  steam  system. 
Two-room  building1,  one  floor,  no  basement,. 

Direct-indirect  room  heater  in  each  room. 
Two-room  building,  one  floor,  with  basement. 

Gravity  furnace  system  with  vent  flues  and  cowls. 

Indirect,    one-pipe    or    two-pipe    steam    system    with    as- 
pirating vent  flues  and  cowls. 

Direct-indirect,  one-pipe  or  two-pipe  steam  system,  with 
aspirating  vent  flues  and  cowls. 
Three-room  building,  one  floor,  with  basement. 

Gravity  furnace  system  with  vent  flues  and  cowls. 

Indirect,    one-pipe   or   two-pipe    steam    system,   with   as- 
pirating vent  flues  and  cowls. 

Direct-indirect,  one-pipe  or  two-pipe  steam  system,  with 
aspirating  vent  flues  and  cowls. 
Four-room  building,  two  floors,  with  basement. 

Gravity  furnace  system  with  vent  flues  and  cowls. 


398  HEATING  AND  VENTILATION 

Indirect  or  direct-indirect  steam  systems,  with  aspirat- 
ing vent  flues  and  cowls. 

Fan  furnace  system  (where  electric  power  is  available). 
Automatic  temperature  control. 

Four-room  building:,  two  Hours  with  basement  rooms  used 
for  school  purposes  but  not  as  laboratories  or  class 
rooms. 

Indirect  or  direct-indirect  steam  system  on  first  and  sec- 
ond floors,  and  direct  system  in  basement;  with  aspirating 
vent  flues  and  cowls.  With  or  without  automatic  tempera- 
ture control. 

Fan-furnace  system  (where  electric  power  is  available). 
Automatic  temperature  control. 

Six-   or  eigrht-room   building:,  with  basement   rooms  used   for 
laboratory  and  school  purposes  other  than  class  rooms. 

Fan-coil  system,  with  electric  power  or  low-pressure 
steam  engine.  Direct  radiation  in  corridors,  toilet  and  wash 
rooms.  Automatic  temperature  control.  Toilets  separately 
ventilated  by  motor  driven  suction  fans. 

Direct-indirect,  vapor  or  low-pressure  steam  system  on 
first  and  second  floors,  and  direct  system  in  the  basement; 
with  aspirating  vent  flues  and  cowls.  With  or  without  auto- 
matic temperature  control. 

Fan-furnace  system  (where  electric  power  is  available). 
Automatic    temperature    control.      Toilets    separately    venti- 
lated by  motor  driven  suction  fans. 
Moderately  large  buildings  with  basement  school  rooms. 

Heat  by  direct  radiation,  mechanical  vacuum  returns; 
ventilate  by  fan-coil  system.  With  or  without  air  condition- 
ing apparatus.  Toilets  separately  ventilated  by  motor  driven 
suction  fans.  Automatic  temperature  control. 

Heat  and  ventilate  by  fan-coil  system.  With  or  without 
air  conditioning  apparatus.  Toilets  separately  ventilated  by 
motor  driven  suction  fans.  Automatic  temperature  control. 
l.:n-m-  buildings  with  basement  school  rooms. 

Heat  by  direct  radiation,  mechanical  vacuum  returns, 
ventilate  by  fan-coil  system.  Air  conditioning  apparatus. 
Toilets  separately  ventilated  by  motor  driven  suction  fans. 
Automatic  temperature  control. 

Heat  and  ventilate  by  fan-coil  system.  Air  conditioning 
apparatus.  Toilets  separately  ventilated  by  motor  driven 
suction  fans. 


APPENDIX 
I. 


GENERAL  TABLES. 
HEATING  AND  VENTILATION. 


Tables  in  body  of  text  are  numbered  in  Roman 
numerals,  those  in  the  Appendixes  are  numbered  in 
Arabic  numerals. 

All  tables  that  are  not  considered  general  are  credited 
and  added  by  permission  of  the  authors. 


TABLE   1. 
Squares,  Cubes,  Sq.  Roots,  Cube  Roots,  Circles. 


No. 

Pi  am. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Circumf. 

Area 

.1 

.010 

.001 

.316 

.464 

.314 

.00785 

.2 

.040 

.008 

.447 

.585 

.628 

.03146 

.3 

.090 

.027 

.548 

.669 

.942 

.07069 

.4 

.160 

.064 

.633 

.737 

1.257 

.12566 

.5 

.250 

.125 

.707 

.794 

1.570 

.19635 

.6 

.360 

.216 

.775 

.843 

1.885 

.28274 

.7 

.490 

.343 

.837 

.888 

2.200 

.38485 

.8 

.640 

.512 

.894 

.928 

2.513 

.50266 

.9 

.810 

.729 

.949 

.965 

2.830 

.63620 

1.0 

1.000 

1.000 

1.000 

1.000 

3.1416 

.7854 

1.1 

1.210 

1.331 

1.0488 

1.0323 

3.456 

.9503 

1.2 

1.440 

1.730 

1.0955 

1.0627 

3.770 

1.1310 

1-.3 

1.690 

2.197 

1.1402 

1.0914 

4.084 

1.3273 

1.4 

1.960 

2.744 

1.1832 

1.1187 

4.398 

1.5304 

1.5 

2.250 

3.375 

1.2247 

1.1447 

4.712 

1.7672 

1.6 

2.560 

4.096 

1.2649 

1.1696 

5.027 

2.0106 

1.7 

2.890 

4.913 

1.3038 

1.1935 

5.341 

2.2698 

1.8 

3.240 

5.832 

1.3416 

1.2164 

5.655 

2.5447 

1.9 

3.610 

6.859 

1.3784 

1.2386 

5.969 

2.8353 

2.0 

4.000 

8.000 

1.4142 

1.2599 

6.283 

3.1416 

2.1 

4.410 

9.261 

1.4491 

1.2806 

6.597 

3.463f> 

2.2 

4.840 

10.648 

1.4832 

1.3006 

6.912 

3.8013 

2.3 

5.290 

12.167 

1.5166 

1.3200 

7.226 

.1548 

2.4 

5.760 

13.824 

1.5492 

1.3389 

7.540 

.5239 

2.5 

6.250 

15.625 

1.5811 

1.3572 

7.854 

.9087 

2.6 

6.760 

17.576 

1.6125 

1.3751 

8.168 

.3093 

2.7 

7.290 

19.683 

1.6432 

1.3925 

8.482 

.7256 

2.8 

7.840 

21.952 

1.6733 

1.4095 

8.797 

6.1575 

2.9 

8.410 

24.389 

1.7029 

1.4260 

9.111 

6.6052 

3.0 

9.000 

27.000 

1.7321 

1.4422 

9.425 

7.0688 

3.1 

9.610 

29.791 

1.7607 

1.4581 

9.739 

7.5477 

3.2 

10.240 

32.768 

1.7889 

1.4736 

10.053 

8.0425 

3.3 

10.890 

35.937 

1.8166 

1.4888 

10.367 

8.5530 

3.4 

11.560 

39.304 

1.8439 

1.5037 

10.681 

9.0792 

3.5 

12.250 

42.875 

1.8708 

1.5183 

10.996 

9.6211 

3.6 

12.960 

46.656 

1.8974 

1.5326 

11.310 

10.179 

3.7 

13.690 

50.653 

1.9235 

1.5467 

11.024 

10.752 

3.8 

14.440 

54.872 

1.9494 

1.5605 

11.938 

11.341 

3.9 

15.210 

59.319 

1.9748 

1.5741 

12.252 

11.946 

4.0 

16.000 

64.000 

2.0000 

1.5870 

12.566 

12.566 

4.1 

16.810 

68.921 

2.0249 

1.6005 

12.881 

13.203 

4.2 

17.640 

74.088 

2.0494 

1.6134 

13.195 

13.854 

4.3 

18.490 

79.507 

2.0736 

1.6261 

13.509 

14.522 

4.4 

19.360 

85.184 

2.0976 

1.6386 

13.823 

15.205 

400 


No. 
Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Circumf. 

Area 

4.5 

20.250 

91.125 

2.1213 

.6510 

14.137 

15.904 

4.6 

21.160 

97.336 

2.1448 

.6631 

14.451 

16.619 

4.7 

22.000 

103.823 

2.1680 

.6751 

14.765 

17.349 

4.8 

23.040 

110.592 

2.1909 

.6869 

15.080 

18.096 

4.9 

24.010 

117.649 

2.2136 

.6985 

15.394 

18.859 

5.0 

25.000 

125.000 

2.2361 

.7100 

15.708 

19.635 

5.1 

26.010 

132.651 

2.2583 

.7213 

16.022 

20.428 

5.2 

27.040 

140.608 

2.2804 

.7325 

16.336 

21.237 

5.3 

28.090 

148.877 

2.3022 

.7435 

16.650 

22.062 

5.4 

29.160 

157.464 

2.3238 

.7544 

16.965 

22.902 

5.5 

30.250 

166.375 

2.3452 

.7652 

17.279 

23.758 

5.6 

31.360 

175.616 

2.3664 

.7760 

17.593 

24.630 

5.7 

32.490 

185.193 

2.3875 

.7863 

17.907 

25.518 

5.8 

33.640 

195.112 

2.4083 

.7967 

18.221 

26.421 

5.9 

34.810 

205.379 

2.4290 

.8070 

18.536 

27.340 

6.0 

36.000 

216.000 

2.4495 

.8171 

18.850 

28.274 

6.1 

37.210 

226.981 

2.4698 

.8272 

19.164 

29.225 

6.2 

38.440 

238.328 

2.4900 

.8371 

19.478 

30.191 

6.3 

39.690 

250.047 

2.5100 

.8469 

19.792 

31.173 

6.4 

40.960 

262.144 

2.5298 

.8566 

20.106 

32.170 

6.5 

42.250 

274.625 

2.5495 

.8663 

20.420 

33.183 

6.6 

43.560 

287.496 

2.5691 

.8758 

20.735 

34.212 

6.7 

44.890 

300.763 

2.5884 

.8852 

21.049 

35.257 

6.8 

46.240 

314.432 

2.6077 

.8945 

21.363 

36.317 

6.9 

47.610 

328.509 

2.6268 

.9038 

21.677 

37.393 

7.0 

49.000 

343.000 

2.6458 

1.9129 

21.991 

38.485 

7.1 

50.410 

357.911 

2.6646 

1.9220 

22.305 

39.592 

7.2 

51.840 

373.248 

2.6833 

1.9310 

22.619 

40.715 

7.3 

53.290 

389.017 

2.7019 

1.9399 

22.934 

41.854 

7.4 

54.760 

405.224 

2.7203 

1.9487 

23.248 

43.008 

7.5 

56.250 

421.875 

2.7386 

1.9574 

23.562 

44.179 

7.6 

57.760 

438.976 

2.7568 

1.9661 

23.876 

45.365 

7.7 

59.290 

456.533 

2.7749 

1.9747 

24.190 

46.566 

7.8 

60.840 

474.552 

2.7929 

1.9832 

24.504 

47.784 

7.9 

62.410 

493.039 

2.8107 

1.9916 

24.819 

49.017 

8.0 

64.000 

512.000 

2.8284 

2.0000 

25.133 

50.266 

8.1 

65.610 

531.441 

2.8461 

2.0083 

25.447 

51.530 

8.2 

67.240 

551.468 

2.8636 

2.0165 

25.761 

52.810 

8.3 

68.890 

571.787 

2.8810 

2.0247 

26.075 

54.106 

8.4 

70.560 

592.704 

2.8983 

2.0328 

26.389 

55.418 

8.5 

72.250 

614.125 

2.9155 

2.0408 

26.704 

56.745 

8.6 

73.960 

636.056 

2.9326 

2.0488 

27.018 

58.088 

8.7 

75.690 

658.503 

2.9496 

2.0567 

27.332 

59.447 

8.8 

77.440 

681.473 

2.9665 

2.0646 

27.646 

60.821 

8.9 

79.210 

704.969 

2.9833 

2.0724 

27.960 

62.211 

401 


No. 
Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Circumf. 

Area 

9.0 

81.000 

729.000 

3.0000 

2.0801 

28.274 

63.617 

9.1 

82.810 

753.571 

3.0166 

2.0878 

28.588 

65.039 

9.2 

84.640 

778.688 

3.0332 

2.0954 

28.903 

66.476 

9.3 

86.490 

804.357 

3.0496 

2.1029 

29.217 

67.929 

9.4 

88.360 

830.584 

3.0659 

2.1105 

29.531 

69.398 

9.5 

90.250 

857.375 

3.0822 

2.1179 

29.845 

70.882 

9.6 

92.160 

884.736 

3.0984 

2.1253 

30.159 

72.382 

9.7 

94.090 

912.673 

3.1145 

2.1327 

30.473 

73.898 

9.8 

96.040 

941.192 

3.1305 

2.1400 

30.788 

75.430 

9.9 

98.010 

970.299 

3.1464 

2.1472 

31.102 

76.977 

10 

100.000 

1000.000 

3.1623 

2.1544 

31.416 

78.540 

11 

121.000 

1331.000 

3.3166 

2.2239 

34.558 

95.033 

12 

144.000 

1728.000 

3.4641 

2.2894 

37.699 

113.097 

13 

169.000 

2197.000 

3.6056 

2.3513 

40.841 

132.732 

14 

196.000 

2744.000 

3.7417 

2.4101 

43.982 

153.938 

15 

225.000 

3375.000 

3.8730 

2.4662 

47.124 

176.715 

16 

256.000 

4096.000 

4.0000 

2.5198 

50.265 

201.062 

17 

289.000 

4913.000 

4.1231 

2.5713 

53.407 

226.980 

18 

324.000 

5832.000 

4.2426 

2.6207 

56.549 

254.469 

19 

361.000 

6859.000 

4.3589 

2.6684 

59.690 

283.529 

20 

400.000 

8000.000 

4.4721 

2.7144 

62.832 

314.159 

21 

441.000 

9261.000 

4.5826 

2.7589 

65.793 

346.361 

22 

484.000 

10648.000 

4.6904 

2.8021 

69.115 

380.133 

23 

529.000 

12167.000 

4.7958 

2.8439 

72.257 

415.476 

24 

576.000 

13824.000 

4.8990 

2.8845. 

75.398 

452.389 

25 

625.000 

15625.000 

5.0000 

2.9241 

78.540 

490.874 

26 

676.000 

17576.000 

5.0990 

2.9625 

81.681 

530.929 

27 

729.000 

19683.000 

5.1962 

3.0000 

84.823 

572.555 

28 

784.000 

21952.000 

5.2915 

3.0366 

87.965 

615.752 

29 

841.000 

24389.000 

5.3852 

3.0723 

91.106 

660.520 

30 

900.000 

27000.000 

5.4772 

3.1072 

94.248 

706.858 

31 

961.000 

29791.000 

5.5678 

3.1414 

97.389 

754.768 

32 

1024.000 

32768.000 

5.6569 

3.1748 

100.531 

804.248 

33 

1089.000 

35037.000 

5.7446 

3.2075 

103.673 

855.299 

34 

1156.000 

39304.000 

5.8310 

3.2396 

106.841 

907.920 

35 

1225.000 

42875.000 

5.9161 

3.2710 

109.956 

962.113 

36 

1296.000 

46656.000 

6.0000 

3.3019 

113.097 

1017.88 

37 

1369.000 

50653.000 

6.0827 

3.3322 

116.239 

1075.21 

38 

1444.000 

54872.000 

6.1644 

3.3620 

119.381 

1134.11 

39 

1521.000 

59319.000 

6.2450 

3.3912 

122.522 

1194.59 

40 

1600.000 

64000.000 

6.3246 

3.4200 

125.66 

1256.64 

41 

1681.000 

68921.000 

6.4031 

3.4482 

128.81 

1320.25 

42 

1764.000 

74088.000 

6.4807 

3.4760 

131.95 

1385.44 

43 

1849.000 

79507.000 

6.5574 

3.5034 

135.09 

1452.20 

44 

1936.000 

85184.000 

6.6333 

3.5303 

138.23 

1520.53 

402 


No. 

Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Circumf  . 

Area 

45 

2025.000 

91125.000 

6.7082 

3.5569 

141.37 

1590.43 

46 

2116.000 

97336.000 

6.7823 

3.5830 

144.51 

1661.90 

47 

2209.000 

103823.000 

6.8557 

3.6088 

147.65 

1734.94 

48 

2304.000 

110592.000 

6.9282 

3.6342 

150.80 

1809.56 

49 

2401.000 

117649.000 

7.0000 

3.6593 

153.94 

1885.74 

50 

2500.000 

125000.000 

7.0711 

3.6840 

157.08 

1963.50 

51 

2601.000 

132651.000 

7.1414 

3.7084 

160.22 

2042.82 

52 

2704.000 

140608.000 

7.2111 

3.7325 

163.36 

2123.72 

53 

2809.000 

148877.000 

7.2801 

3.7563 

166.50 

2206.18 

54 

2916.000 

157464.000 

7.3485 

3.7798 

169.65 

2290.22 

55 

3025.000 

166375.000 

7.4162 

3.8030 

172.79 

2375.83 

50 

3136.000 

175616.000 

7.4833 

3.8259 

175.93 

2463.01 

57 

3249.000 

185193.000 

7.5498 

3.8485 

179.07 

2551.76 

58 

3364.000 

195112.000 

7.6158 

3.8709 

182.21 

2642.08 

59 

3481.000 

205379.000 

7.6811 

3.8930 

185.35 

2733.97 

60 

3600.000 

216000.000 

7.7460 

3.9149 

188.50 

2827.43 

61 

3721.000 

226981.000 

7.8102 

3.9365 

191.64 

2922.47 

62 

3844.000 

238328.000 

7.8740 

3.9579 

194.78 

3019.07 

63 

3969.000 

250047.000 

V.9373 

3.9791 

197.92 

3117.25 

64 

4096.000 

262144.000 

8.0000 

4.0000 

201.06 

3216.99 

65 

4225.000 

274625.000 

8.0623 

4.0207 

204.20 

3318.31 

66 

4356.000 

287496.000 

8.1240 

4.0412 

207.34 

3421.19 

67 

4489.000 

300763.000 

8.1854 

4.0615 

210.49 

3525.65 

68 

4624.000 

314432.000 

8.2462 

4.0817 

213.63 

3631.68 

69 

4761.000 

328509.000 

8.3066 

4.1016 

216.77 

3739.28 

70 

4900.000 

343000.000 

8.3666 

4.1213 

219.91 

3848.45 

71 

5041.000 

357911.000 

8.4261 

4.1408 

223.05 

3959.19 

72 

5184.000 

373248.000 

8.4853 

4.1602 

226.19 

4071.50 

73 

5329.000 

389017.000 

8.5440 

4.1793 

229.34 

4185.39 

74 

5476.000 

405224.000 

8.6023 

4.1983 

232.48 

4300.84 

75 

5625.000 

421875.000 

8.6603 

4.2172 

235.62 

4417.86 

76 

5776.000 

438976.000 

8.7178 

4.2358 

238.76 

4536.46 

77 

5929.000 

456533.000 

8.7750 

4.2543 

241.90 

4656.63 

78 

6084.000 

474552.000 

8.8318 

4.2727 

245.04 

4778.36 

79 

6241.000 

498039.000 

8.8882 

4.2908 

248.19 

4901.67 

80 

6400.000 

512000.000 

8.9443 

4.3089 

251.33 

5026.55 

81 

6561.000 

531441.000 

9.0000 

4.3267 

254.47 

5153.00 

82 

6724.000 

551368.000 

9.0554 

4.3445 

257.61 

5281.02 

83 

6889.000 

571787.000 

9.1104 

4.3621 

260.75 

5410.61 

84 

7056.000 

592704.000 

9.1652 

4.3795 

263.89 

5541.77 

85 

7225.000 

614125.000 

9.2195 

4.3968 

267.04 

5674.50 

86 

7396.000 

636056.000 

9.2736 

4.4140 

270.18 

5808.80 

87 

7569.000 

658503.000 

9.3274 

4.4310 

273.32 

5944.68 

88 

7744.000 

681472.000 

9.3808 

4.4480 

276.46 

6082.12 

89 

7921.000 

704969.000 

9.4340 

4.4647 

279.60 

6221.14 

403 


No. 
Diam. 

Square 

Cube 

Sq. 
Root 

Cube 
Root 

Circle 

Circumf. 

Area 

90 

8100.000 

729000.000 

9.4868 

4.4814 

282.74 

6361.73 

91 

8281.000 

753571.000 

9.5394 

4.4979 

285.88 

6503.88 

92 

8464.000 

778688.000 

9.5917 

4.5144 

289.03 

6647.61 

93 

8649.000 

804357.000 

9.6437 

4.5307 

292.17 

6792.91 

94 

8836.000 

830584.000 

9.6954 

4.5468 

295.31 

6939.78 

95 

9025.000 

857375.000 

9.7468 

4.5629 

298.45 

7088.22 

96 

9216.000 

884736.000 

9.7980 

4.5789 

301.59 

7238.23 

97 

9409.000 

912673.000 

9.8489 

4.5947 

304.73 

7389.81 

98 

9804.000 

941192.000 

9.8995 

4.6104 

307.88 

7542.96 

99 

9901.000 

•  970299.000 

9.9499 

4.6261 

311.02 

7697.69 

100 

10000.000 

1000000.000 

10.0000 

4.6416 

314.16 

7853.98 

106 

11025.000 

1157625.000 

10.2470 

4.7177 

329.87 

8659.01 

110 

12100.000 

1331000.000 

10.4881 

4.7914 

345.58 

9503.32 

115 

13225.000 

1520875.000 

10.7238 

4.8629 

361.28 

10386.89 

120 

14400.000 

1728000.000 

10.9545 

4.9324 

376.99 

11309.73 

125 

15625.000 

1953125.000 

11.1803 

5.0000 

392.70 

12271.85 

130 

16900.000 

2197000.000 

11.4018 

5.0658 

408.41 

13273.23 

135 

18225.000 

2460375.000 

11.6190 

5.1299 

424.12 

14313.88 

140 

19600.000 

2744000.000 

11.8322 

5.1925 

439.82 

15393.80 

145 

21025.000 

3048625.000 

12.0416 

5.2536 

455.53 

16513.00 

150 

22500.000 

3375000.000 

12.2474 

5.3133 

471.24 

17671.46 

155 

24025.000 

3723875.000 

12.4499 

5.3717 

486.95 

18869.19 

160 

25600.000 

4096000.000 

12.6491 

5.4288 

502.65 

20106.19 

165 

27225.000 

4492125.000 

12.8452 

5.4848 

518.36 

21382.46 

170 

28900.000 

4913000.000 

13.0384 

5.5397 

534.07 

22698.01 

175 

30625.000 

5359375.000 

13.22S8 

5.5934 

549.78 

24052.82 

180 

32400.000 

5832000.000 

13.4164 

5.6462 

565.49 

25446.90 

185 

34225.000 

6331625.000 

13.6015 

5.6980 

581.19 

26880.25 

190 

36100.000 

6859000.000 

13.7840 

5.7489 

596.90 

28352.87 

195 

38025.000 

7414875.000 

13.9642 

5.7989 

612.61 

29864.77 

200 

40000.000 

8000000.000 

14.1421 

5.8480 

628.32 

31415.93 

205 

42025.000 

8615125.000 

14.3178 

5.8964 

644.03 

33006.36 

210 

44100.000 

9261000.000 

14.4914 

5.9439 

659.73 

34636.06 

215 

46225.000 

9938375.000 

14.6629 

5.9907 

675.44 

36305.03 

220 

48400.000 

10648000.000 

14.8324 

6.0368 

691.15 

38013.27 

225 

50625.000 

11390625.000 

15.0000 

6.0822 

706.86 

39760.78 

230 

52900.000 

12167000.000 

15.1&58 

6.1269 

722  .  57 

41547.56 

235 

55225.000 

12977875.000 

15.3297 

6.1710 

738.27 

43373.61 

240 

57600.000 

13824000.000 

15.4919 

6.2145 

753.98 

45238.93 

245 

60025.000 

14706125.000 

15.6525 

6.2573 

769.69 

47143.52 

250 

62500.000 

15625000.000 

15.8114 

6.2996 

7&5.40 

49087.39 

255 

65025.000 

16581375.000 

15.9687 

6.3413 

801.11 

51070.52 

260 

67600.000 

17576000.000 

16.1245 

6.3825 

816.81 

53092.92 

265 

70225.000 

18609625.000 

16.2788 

6.4232 

832.52 

55154.59 

270 

72900.000 

19683000.000 

16.4317 

6.4633 

848.23 

57255.53 

404 


No. 
Diam. 

Square 

Cube 

Sq. 
Eoot 

Cube 
Root 

Circle 

C'ircumf  . 

Area 

275 

75625.000 

20796875.000 

16.5831 

6.5030 

863.94 

59395.74 

280 

78400.000 

21952000.000 

16.7332 

6.5421 

879.65 

61575.22 

285 

81225.000 

23149125.000 

16.8819 

6.5808 

895.35 

63793.97 

290 

84100.000 

24389000.000 

17.0294 

6.6191 

911.06 

66061.99 

295 

87025.000 

25672375.000 

17.1756 

6.6569 

926.77 

68349.28 

300 

90000.000 

27000000.000 

17.3205 

6.6943 

942.48 

70685.83 

305 

93025.000 

28372625.000 

17.4642 

6.7313 

958.19 

73061.66 

310 

96100.000 

29791000.000 

17.6068 

6.7679 

973.89 

75476.76 

315 

99225.000 

31255875.000 

17.7482 

6.8041 

989.60 

77931.13 

320 

102400.000 

32768000.000 

17.8885 

6.8399 

1005.31 

80424.77 

325 

105625.000 

34328125.000 

18.0278 

6.8753 

1021.02 

82957.68 

330 

108900.000 

35937000.000 

18.1659 

6.9104 

1036.73 

85529.86 

335 

112225.000 

37595375.000 

18.3030 

6.9451 

1052.43 

88141.31 

340 

115600.000 

39304000.000 

18.4391 

6.9795 

1068.14 

90792.03 

345 

119025.000 

41063625.000 

18.5742 

7.0136 

1083.85 

93482.02 

350 

122500.000 

42875000.000 

18.7083 

7.0473 

1099.56 

96211.28 

355 

126025.000 

44738875.000 

18.8414 

7.0807 

1115.27 

98979.80 

360 

129600.000 

46656000.000 

18.9737 

7.1138 

1130.97 

101787.60 

365 

133225.000 

48627125.000 

19.1050 

7.1466 

1146.68 

104634.67 

370 

136900.000 

50653000.000 

19.2354 

7.1791 

1162.39 

107521.01 

375 

140625.000 

52734375.000 

19.3649 

7.2112 

1178.10 

110446.62 

380 

144400.000 

54872000.000 

19.4936 

7.2432 

1193.81 

113411.49 

385 

148225.000 

57066625.000 

19.6214 

7.2748 

1209.51 

116415.64 

390 

152100.000 

59319000.000 

19.7484 

7.3061 

1225.22 

119459.06 

395 

156025.000 

61629875.000 

19.8746 

7.3372 

1240.93 

122541.75 

400 

160000.000 

64000000.000 

20.0000 

7.3681 

1256.64 

125663.71 

405 

164025.000 

66430125.000 

20.1246 

7.3986 

1272.35 

128824.93 

410 

168100.000 

68921000.000 

20.2485 

7.4290 

1288.05 

132025.43 

415 

172225.000 

71473375.000 

20.3715 

7.4590 

1303.76 

135265.20 

420 

176400.000 

74088000.000 

20.4939 

7.4889 

1319.47 

138544.24 

425 

180825.000 

76765625.000 

20.6155 

7.5185 

1335.18 

141862.54 

430 

184900.000 

79507000.000 

20.7364 

7.5478 

1350.88 

145220.12 

435 

189225.000 

82312875.000 

20.8567 

7.5770 

1366.59 

148616.97 

440 

193600.000 

85184000.000 

20.9762 

7.6059 

1382.30 

152053.08 

445 

198025.000 

88121125.000 

21.0950 

7.6346 

1398.01 

155528.47 

450 

202500.000 

91125000.000 

21.2132 

7.6631 

1413.72 

159043.13 

455 

207025.000 

94196375.000 

21.3307 

7.6914 

1429.42 

162597.05 

460 

211600.000 

97336000.000 

21.4476 

7.7194 

1445.13 

166190.25 

465 

216225.000 

100544625.000 

21.5639 

7.7473 

1460.84 

169822.72 

470 

220900.000 

103823000.000 

21.6795 

7.7750 

1476.55 

173494.45 

475 

225625.000 

107171875.000 

21.7945 

7.8025 

1492.26 

177205.46 

480 

230400.000 

110592000.000 

21.9089 

7.8297 

1507.96 

180955.74 

485 

235225.000 

114084125.000 

22.0227 

7.8568 

1523.67 

184745.28 

490 

240100.000 

117649000.000 

22.1359 

7.8837 

1539.38 

188574.10 

495 

245025.000 

121287375.000 

22.2486 

7.9105 

1555.09 

192442.18 

500 

250000.000 

125000000.000 

22.3607 

7.9370 

1570.80 

196349.54 

405 


TABLE   2. 
Trigonometric  Functions. 


Angle, 

Sine 

Tangent 

Angle, 

Sine 

Tangent 

degrees 

degrees 

0.0 

0.00000 

0.00000 

90.0 

47.5 

0.73728 

1.0913 

42.5 

2.5 

0.04362 

0.04362 

87.5 

50.0 

0.76604 

1.1917 

40.0 

5.0 

0.08716 

0.08749 

85.0 

52.5 

0.79335 

1.3032 

37.5 

7.5 

0.13053 

0.13165 

82.5 

55.0 

0.81915 

1.4281 

35.0 

10.0 

0.17365 

0.17633 

80.0 

57.5 

0.84339 

1.5697 

32.5 

12.5 

0.21644 

0.22169 

77.5 

60.0 

0.86603 

1.7321 

30.0 

15.0 

0.25882 

0.26795 

75.0 

62.5 

0.88701 

1.9210 

27.5 

17.5 

0.30071 

0.31530 

72.5 

65.0 

0.90631 

2.1445 

25.0 

20.0 

0.34202 

0.36397 

70.0 

67.5 

0.92388 

2.4142 

22.5 

22.5 

0.382C3 

0.41421 

67.5 

70.0 

0.93969 

2.7474 

20.0 

25.0 

0.42262 

0.46631 

65.0 

72.5 

0.95372 

3.1716 

17.5 

27.5 

0.46175 

0.52057 

62.5 

75.0 

0.96593 

3.7321 

15.0 

30.0 

0.50000 

0.57735 

60.0 

77.5 

0.97630 

4.5107 

12.5 

32.5 

0.53730 

0.63707 

57.5 

80.0 

0.98481 

5.6713 

10.0 

35.0 

0.57358 

0.70021 

55.0 

82.5 

0.99144 

7.5958 

7.5 

37.5 

0.60876 

0.76733 

52.5 

85.0 

0.99619 

11.430 

5.0 

40.0 

0.64279 

0.83910 

50.0 

87.0 

0.99863 

19.081 

3.0 

42.5 

0.67559 

0.91633 

47.5 

88.5 

0.99966 

38.188 

1.5 

45.0 

0.70711 

1.0000 

45.0 

90.0 

1.0000 

Infinite 

0.0 

Cosine 

Cotan- 

Angle, 

Cosine 

Cotan- 

Angle, 

gent 

degrees 

gent 

degrees 

TABLE   3. 
Equivalents  of  Compound  Units. 


1  Ib.  per  sq.  in. 


1  oz.  per  sq.  in. 


1  in.  of  water  at  62°  F.        = 


1  in.  of  water  at  32°  F. 


1  in.  of  mercury  at  62°  F. 


1  ft.  of  air  at  32°  F. 


{27.71      in.  of  water  at  62°  F. 
2.0355  in.  of  mercury  at  32°  F. 
2.0416  in.  of  mercury  at  62°  F. 
2.3090  ft.  of  water  at  62°  F. 
1784.          ft.  of  air  at  32°  F. 

\  0.1276  in.  of  mercury  at  62°  F. 
1^1.732    in.  of  water  at  62°  F. 

fO. 03609  Ib.  or  .5574  oz.  per  s.  in. 
—  -J5.196     Ibs.  per  sq.  ft. 

Lo.0736    in.  of  mercury  at  62°  F. 


5.2021      Ibs.  per  sq.  ft. 
0.036125  Ib.  per  sq.  in. 

).491  Ib.  or  7.86  oz.  per  sq.  in. 
L.132  ft.  of  water  at  62°  F. 
5.58    in.  of  water  at  62°  F. 


/O. 
\0. 


. 0005606  Ib.  per  sq.  fn. 
015534  in.  of  water  at  62°  F. 


TABLE   4. 
Properties  of  Saturated  Steam. < 


Abs. 
pres  .  , 
lb., 

P 

Temp., 
cleg, 
fahr., 
t 

Sp.  vol., 
cu.  ft. 
per  lb., 
v" 

Density, 
lb.  per 
cu.  ft., 
1/t?" 

Heat 
of  the 
liquid, 
*' 

Latent 
heat  of 
evap  .  , 
r 

Heat 

content 
of  steam, 
i" 

1 

101.83 

333.0 

0.00300 

69.8 

1034.6 

1104.4 

2 

126.15 

173.5 

0.00576 

94.0 

1021.0 

1115.0 

3 

141.52 

118.5 

0.00845 

109.4 

1012.3 

1121.6 

4 

153.01 

90.5 

0.01107 

120.9 

1005.7 

1126.5 

5 

162.28 

73.33 

0.01364 

130.1 

1000.3 

1130.5 

6 

170.06 

61.89 

0.01616 

137.9 

995.8 

1133.7 

7 

176.85 

53.56 

0.01867 

144.7 

991.8 

1136.5 

8 

182.86 

47.27 

0.02115 

150.8 

988.2 

1139.0 

9 

188.27 

42.36 

0.02361 

156.2 

985.0 

1141.1 

10 

193.22 

38.38 

0.02606 

161.1 

982.0 

1143.1 

11 

197.75 

35.10 

0.02849 

165.7 

979.2 

1144.9 

12 

201.96 

32.36 

0.03090 

169.9 

976.6 

1146.5 

13 

205.87 

30.03 

0.03330 

173.8 

974.2 

1148.0 

14 

209.55 

28.02 

0.03569 

177.5 

971.9 

1149.4 

14.7 

212.00 

26.79 

0.03732 

180.0 

970.4 

1150.4 

15 

213.0 

26.27 

0.03806 

181.0 

969.7 

1150.7 

16 

216.3 

24.79 

0.04042 

184.4 

967.6 

1152.0 

17 

219.4 

23.38 

0.04277 

187.5 

965.6 

1153.1 

18 

222.4 

22.16 

0.04512 

190.5 

963.7 

1154.2 

19 

225^2 

21.07 

0.04746 

193.4 

961.8 

1155.2 

20 

228.0 

20.08 

0.04980 

196.1 

960.0 

1156.2 

21 

230.6 

19.18 

0.05213 

198.8 

958.3 

1157.1 

221 

233.1 

18.37 

0.05445 

201.3 

956.7 

1158.0 

28" 

235.5 

17.62 

0.05676 

203.8 

955.1 

1158.8 

24 

237.8 

16.93 

0.05907 

206.1 

953.5 

1159.6 

25 

240.1 

16.30 

0.0614 

208.4 

952.0 

1160.4 

26 

242.2 

15.72 

0.0636 

210.6 

950.6 

1161.2 

27 

244.4 

15.18 

0.0659 

212.7 

949.2 

1161.9 

28 

246.4 

14.67 

0.0682 

214.8 

947.8 

1162.6 

29 

248.4 

14.19 

0.0705 

216.8 

946.4     , 

1163.2 

30 

250.3 

13.74 

0.0728 

218.8 

945.1 

1163.9 

31 

252.2 

13.32 

0.0751 

220.7 

943.8 

1164.5 

32 

254.1 

12.93 

0.0773 

222.6 

942.5 

1165.1 

33 

255.8 

12.57 

0.0795 

224.4 

941.3 

1165.7 

34 

257.6 

12.22 

0.0818 

226.2 

940.1 

1166.3 

35 

259.3 

11.89 

0.0841 

227.9 

938.9 

1166.8 

36 

261.0 

11.58 

0.0863 

229.6 

937.7 

1167.3 

37 

262.6 

11.29 

0.0886 

231.3 

936.6 

1167.8 

38 

264.2 

11.01 

0.0908 

232.9 

935.5 

1168.4 

39 

265.8 

10.74 

0.0931 

234.5 

934.4 

1168.9 

40 

267.3 

10.49 

0.0953 

236.1 

933.3 

1169.4 

41 

268.7 

10.25 

0.0976 

237.6 

932.2 

1169.8 

42 

270.2 

10.02 

0.0998 

239.1 

931.2 

1170.3 

43 

271.7 

9.80 

0.1020 

240.5 

930.2 

1170.7 

44 

273.1 

9.59 

0.1043 

242.0 

929.2 

1171.2 

45 

274.5 

9.39 

0.1065 

243.4 

928.2 

1171.6 

46 

275.8 

9^20 

0.1087 

244.8 

927.2 

1172.0 

47 

277.2 

9.02 

0.1109 

246.1 

926.3 

1172.4 

48 

278.5 

8.84 

0.1131 

247.5 

925.3 

1172.8 

49 

279.8 

8.67 

0.1153 

248.8 

924.4 

1173.2 

*  Marks  and  Davis,  Handbook. 


407 


Aba. 
pres., 
lb., 

P 

Temp., 
deg. 
fahr., 
* 

Sp.  vol., 
cu.  ft. 
perlb., 

V" 

Density, 
lb.  per 
cu.  ft., 
1/v" 

Heat 
of  the 
liquid, 
V 

Latent 
heat  of 
evap., 
r 

Heat 
content 
of  steam, 

50 

281.0 

8.51 

0.1175 

250.1 

923.5 

1173.6 

51 

282.3 

8.35 

0.1197 

251.4 

922.6 

1174.0 

52 

283.5 

8.20 

0.1219 

252.6 

921.7 

1174.3 

53 

284.7 

8.05 

0.1241 

253.9 

920.8 

1174.7 

54 

285.9 

7.91 

0.1263 

2.55.1 

919.9 

1175.0 

55 

287.1 

7.78 

0.1285 

256.3 

919.0 

1175.4 

56 

288.2 

7.65 

0.1307 

257.5 

918.2 

1175.7 

57 

289.4 

7.52 

0.1329 

258.7 

917.4 

1176.0 

58 

290.5 

7.40 

0.1350 

259.8 

916.5 

1176.4 

59 

291.6 

7.28 

0.1372 

261.0 

915.7 

1176.7 

60 

292.7 

7.17 

0.1394 

262.1 

914.9 

1177.0 

61 

293.8 

7.06 

0.1416 

263.2 

914.1 

1177.3 

62 

294.9 

6.95 

0.1438 

264.3 

913.3 

1177.6 

63 

295.9 

6.85 

0.1460 

265.4 

912.5 

1177.9 

64 

297.0 

6.75 

0.1482 

266.4 

911.8 

1178.2 

65 

298.0 

6.65 

0.1503 

267.5 

911.0 

1178.5 

66 

299.0 

6.56 

0.1525 

268.5 

910.2 

1178.8 

67' 

300.0 

6.47 

0.1547 

269.6 

909.5 

1179.0 

68 

301.0 

6.38 

0.1569 

270.6 

908.7 

1179.3 

69 

302.0 

6.29 

0.1590 

271.6 

908.0 

1179.6 

70 

302.9 

6.20 

0.1612 

272.6 

907.2 

1179.8 

71 

303.9 

6.12 

0.1634 

273.6 

906.5 

1180.1 

72 

304.8 

6.04 

0.1656 

274.5 

905.8 

1180.4 

73 

305.8 

5.96 

0.1678 

275.5 

905.1 

1180.6 

74 

306.7 

5.89 

0.1699 

276.5 

904.4 

1180.9 

75 

307.6 

5.81 

0.1721 

277.4 

903.7 

1181.1 

76 

308.5 

5.74 

0.1743 

278.3 

903.0 

1181.4 

77 

309.4 

5.67 

0.1764 

279.3 

902.3 

1181.6 

78 

310.3 

5.60 

0.1786 

280.2 

901.7 

1181.8 

79 

311.2 

5.54 

0.1808 

281.1 

901.0 

1182.1 

80 

312.0 

5.47 

0.1829 

282.0 

900.3 

1182.3 

81 

312.9 

5.41 

0.1851 

282.9 

899.7 

1182.5 

82 

313.8 

5.34 

0.1873 

283.8 

899.0 

1182.8 

83 

314.6 

5.28 

0.1894 

284.6 

.898.4 

1183.0 

84 

315.4 

5.22 

0.1915 

285.5 

897^7 

1183.2 

85 

316.3 

5.16 

0.1937 

286.3 

897.1 

1183.4 

86 

317.1 

5.10 

0.1959 

287.2 

896.4 

1183.6 

87 

317.9 

5.05 

0.1980 

288.0 

895.8 

1183.8 

88 

318.7 

5.00 

0.2001 

288.9 

895.2 

1184.0 

89 

319.5 

4.94 

0.2023 

289.7 

894.6 

1184.2 

90 

320.3 

4.89 

0.2044 

290.5 

893.9 

1184.4 

91 

321.1 

4.84 

0.2065 

291.3 

893.3 

1184.6 

92 

321.8 

4.79 

0.2087 

292.1 

892.7 

1184.8 

93 

322.6 

4.74 

0.2109 

292.9 

892.1 

1185.0 

94 

323.4 

4.69 

0.2130 

293.7 

891.5 

1185.2 

95 

324.1 

4.65 

0.2151 

294.5 

890.9 

1185.4 

96 

324.9 

4.60 

0.2172 

295.3 

890.3 

1185.6 

97 

325.6 

4.56 

0.2193 

296.1 

889.7 

1185.8 

98 

326.4 

4.51 

0.2215 

296.8 

889.2 

1186.0 

99 

327.1 

4.47 

0.2237 

297.6 

888.6 

1186.2 

Abs. 
pres., 
lb., 

P 

Temp., 
deg. 
fahr., 
t 

Sp.  vol., 
cu.  ft. 
per  lb  .  , 
v" 

Density, 
lb.  per 
cu.  ft., 

w 

Heat 
of  the 
liquid, 
V 

Latent 
heat  of 
evap., 
r 

Heat 
content 
of  steam, 
i" 

100 

327.8 

4.429 

0.2258 

298.3 

888.0 

1186.3 

102 

329.3 

4.347 

0.2300 

299.8 

886.9 

1186.7 

104 

330.7 

4.268 

0.2343 

301.3 

885.8 

1187.0 

106 

332.0 

4.192 

0.2386 

302.7 

884.7 

1187.4 

108 

333.4 

4.118 

0.2429 

304.1 

883.6 

1187.7 

110 

334.8 

4.047 

0.2472 

305.5 

882.5 

1188.0 

112 

336.1 

3.978 

0.2514 

306.9 

881.4 

1188.4 

114 

337.4 

3.912 

0.2556 

308.3 

880.4 

1188.7 

116 

338.7 

3.848 

0.2599 

309.6 

879.3 

1189.0 

118 

340.0 

3.786 

0.2641 

311.0 

878.3 

1189.3 

120 

341.3 

3.726 

0.2683 

312.3 

877.2 

1189.6 

122 

342.5 

3.668 

0.2726 

313.6 

876.2 

1189.8 

124 

343.8 

3.611 

0.2769 

314.9 

875.2 

1190.1 

126 

345.0 

3.556 

0.2812 

316.2 

874.2 

1190.4 

128 

346.2 

3.504 

0.2854 

317.4 

873.3 

1190.7 

130 

347.4 

3.452 

0.2897 

318.6 

872.3 

1191.0 

132 

348.5 

3.402 

0.2939 

319.9 

871.3 

1191.2 

134 

349.7 

3.354 

0.2981 

321.1 

870.4 

1191.5 

136 

350.8 

3.308 

0.3023 

322.3 

869.4 

1191.7 

138 

352.0 

3.263 

0.3065 

323.4 

868.5 

1192.0 

140 

353.1 

3.219 

0.3107 

324.6 

867.6 

1192.2 

142 

354.2 

3.175 

0.3150 

325.8 

866.7 

1192.5 

144 

355.3 

3.133 

0.3192 

326.9 

865.8 

1192.7 

146 

356.  S 

3.092 

0.3234 

328.0 

864.9 

1192.9 

148 

357.4 

3.052 

0.3276 

329.1 

864.0 

1193.2 

150 

358.5 

3.012 

0.3320 

330.2 

863.2 

.  1193.4 

152 

359.5 

2.974 

0.3362 

331.4 

862.3 

1193.6 

154 

360.5 

2.938 

0.3404 

332.4 

861.4 

1193.8 

156 

361.6 

2.902 

0.3446 

333.5 

860.6 

1194.1 

158 

362.6 

2.868 

0.3488 

334.6 

859.7 

1194.3 

160 

363.6 

2.834 

0.3529 

335.6 

858.8 

1194.5 

162 

364.6 

2'.  801 

0.3570 

336.7 

858.0 

1194.7 

164 

365.6 

2.769 

0.3612 

337.7 

857.2 

1194.9 

166 

366,5 

2.737 

0.3654 

338.7 

856.4 

1195.1 

168 

367.5 

2.706 

0.3696 

339.7 

855.5 

1195.3 

170 

368.5 

2.675 

0.3738 

340.7 

854.7 

1195.4 

172 

369^4 

2.645 

0.3780 

341.7 

853.9 

1195.6 

174 

370.4 

2.616 

0.3822 

342.7 

853.1 

1195.8 

176 

371.3 

2.588 

0.3864 

343.7 

852.3 

1196.0 

178 

372.2 

2.560 

0.3906 

344.7 

851.5 

1196.2 

180 

373.1 

2.533 

0.3948 

345.6 

850.8 

1196.4 

182 

374.0 

2.507 

0.3989 

346.6 

850.0 

1196.6 

184 

374.9 

2.481 

0.4031 

347.6 

849.2 

1196.8 

186 

375.8 

2.455 

0.4073 

348.5 

848.4 

1196.9 

188 

376.7 

2.430 

0.4115 

349.4 

847.7 

1197.1 

190 

377.6 

2.406 

0.4157 

350.4 

846.9 

1197.3 

192 

378.5 

2.381 

0.4199 

351.3 

846.1 

1197.4 

194 

379.3 

2.358 

0.4241 

352.2 

845.4 

1197.6 

196 

380.2 

2.335 

0.4283 

353.1 

844.7 

1197.8 

198 

381.0 

2.312 

0.4325 

354.0 

843.9 

1197.9 

409 


Abs. 

Temp  .  , 

Sp.  vol., 

Density, 

Heat 

Latent 

Heat 

pres  .  , 

deg. 

cu.  ft. 

lb.  per 

of  the 

heat  of 

content 

lb., 

fahr., 

perlb., 

cu.  ft., 

liquid, 

evap  .  , 

of  steam, 

P 

t 

v" 

1/t?" 

V 

r 

i" 

200 

381.9 

2.290 

0.437 

354.9 

843.2 

1198.1 

205 

384.0 

2.237 

0.447 

357.1 

841.4 

1198.5 

210 

386.0 

2.187 

0.457 

859.2 

839.6 

1198.8 

215 

388.0 

2.138 

0.468 

361.4 

837.9 

1199.2 

220 

389.9 

2.091 

0.478 

363.4 

836.2 

1199.6 

225 

391.9 

2.046 

0.489 

365.5 

834.4 

1199.9 

230 

393.8 

2.004 

0.499 

367.5 

832.8 

1200.2 

235 

895.6 

1.964 

0.509 

369.4 

831.1 

1200.6 

240 

397.4 

1.924 

0.520 

371.4 

829.5 

1200.9 

245 

35)9.3 

1.887 

0.530 

373.3 

827.9 

1201.2 

250 

401.1 

1.850 

0.541 

375.2 

826.3 

1201.5 

260 

404.5 

1.782 

0.561 

378.9 

823.1 

1202.1 

270 

407.9 

1.718 

0.582 

382.5 

820.1 

120-2.fi 

280 

411.2 

1.658 

0.603 

386.0 

817.1 

1203.  1 

290 

414.4 

1.602 

0.624 

389.4 

814.2 

1203.6 

300 

417.5 

1.551 

0.645  . 

892,7 

811.3 

1204.1 

350 

431.9 

1.334 

0.750 

406.  2 

797.8 

1206.1 

400 

444.8 

1.17 

0.80 

422.0 

786.0 

1208.0 

450 

456.5 

1.04 

0.96 

435.0 

774.0 

1209.0 

500 

467.3 

0.93 

1.08 

448.0 

762.0 

1210.0 

660 

486.  G 

0.76 

1.32 

469.0 

741.0 

1210.0 

410 


e  =   2.7182818 


TABLE   5. 
Naiierian  Logarithms. 

Log  e  =   0.4342945 


=  M. 


1.0 

0.0000 

4.1 

1.4110 

7.2 

1.9741 

1.1 

0.0953 

4.2 

1.4351 

7.3 

1.9879 

1.2 

0.1823 

4.3 

1.4586 

7.4 

2.0015 

1.3 

0.2624 

4.4 

1.4816 

7.5 

2.0149 

1.4 

0.3365 

4.5 

1.5041 

7.6 

2.0281 

1.5 

0.4055 

4.6 

1.5261 

7.7 

2.0412 

1.6 

0.4700 

4.7 

1.5476 

7.8 

2.0541 

1.7 

0.5306 

4.8 

1.5686 

7.9 

2.0669 

1.8 

0.5878 

4.9 

'  1.5892 

8.0 

2.0794 

1.9 

0.6419 

5.0 

1.6094 

8.1 

2.0919 

•  2.0 

0.6931 

5.1 

1.6292 

8.2 

2.1041 

2.1 

0.7419 

5.2 

1.6487 

8.3 

2.1163 

2.2 

0.7885 

5.3 

1.6677 

8.4 

2.1282 

2.3 

0.8329 

5.4 

1.6864 

8.5 

2.1401 

2.4 

0.8755 

5.5 

1.7047 

8.6 

2.1518 

2.5 

0.9163 

5.6 

1.7228 

8.7 

3.1633 

2.6 

0.9555 

5.7 

1.7405 

8.8 

2.1748 

2.7 

0.9933 

5.8 

1.7579 

8.9 

2.1861 

2.8 

1.0296 

5.9 

1.7750 

9.0 

2.1972 

2.9 

1.0647 

6.0 

1.7918 

9.1 

2.2083 

3.0 

1.0986 

6.1 

.8083 

9.2 

2.2192 

3.1 

1.1312 

6.2 

.8245 

9.3 

2.2300 

3.2 

.1632 

6.3 

.8405 

9.4 

2.2407 

3.3 

.1939 

6.4 

.8563 

9.5 

2.2513 

3.4 

.2238 

6.5 

.8718 

9.6 

2.2618 

3.5 

.2528 

6.6 

.8871 

9.7 

2.2721 

3.6 

.2809 

6.7 

.9021 

9.8 

2.2824 

3.7 

.3083 

6.8 

.9169 

9.9 

2.2925 

3.8 

.3350 

6.9 

.9315 

10.0 

2.3026 

3.9 

.3610 

7.0 

.9459 

4.0 

.3863 

7.1 

.9601 

TABLE   6. 
"Water  Conversion  Factors.* 


U.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 
Cubic  inches  of  water  (39.1°) 
Cubic  inches  of  water  (39.1°) 
Cubic  inches  of  water  (39.1°) 
Cubic  feet  of  water  (39.1") 
Cubic  feet  of  water  (39.1") 
Cubic  feet  of  water  (39.1") 
Pounds  of  water 
Pounds  of  water 
Pounds  of  water 

X 
X 
X 
X 
X 

x 

X 

X 
X 

x 

X 
X 
X 

8.33 

0.13368 
231.00000 
3.78 
0.036024 
0.004329 
0.576384 
62.425 
7.48 
0.028 
27.72 
0.01602 
0.12 

_ 

pounds, 
cubic  feet, 
cubic  inches, 
liters, 
pounds. 
U.  S.  gallons, 
ounces  . 
pounds. 
U.  S.  gallons, 
tons, 
cubic  inches, 
cubic  feet. 
U.  S.  gallons. 

*  American  Machinist  Hand  Book. 


411 


TABLE   7. 
Volume   and   Weight  of  Dry  Air  at  Different   Temperatures.* 

Under   a   constant    atmospheric    pressure   of   29.92    inches    of 
mercury,  the  volume  at  32°  F.  being  1. 


Temp, 
deg.  F. 

Volume 

Weight 
per  cu.  ft. 

Temp, 
deg.  F. 

Volume 

Weight 
per  cu.  ft. 

0 

.935 

.0864 

500 

1.954 

.0413 

12 

.960 

.0842 

552 

2.056 

.0385 

22 

.980 

.0824 

600 

2.150 

.0376 

32 

1.000 

.0807 

&50 

2.260 

.0357 

42 

1.020 

.0791 

700 

2.362 

.0338 

52 

1.041 

.0776 

750 

2.465 

.0328 

62 

1.061 

.0761 

800 

2.566 

.0315 

72 

1.082 

.0747 

850 

2.668 

.0303 

82 

1.102 

.0733 

900 

2.770 

.0292 

92 

1.122 

.0720 

950 

2.871 

.0281 

102 

.143 

.0707 

1000 

2.974 

.0268 

112 

.163 

.0694 

1100 

3.177 

.0254 

122 

.184 

.0682 

1200 

3.381 

.0239 

132 

.204 

.0671 

1300 

3.584 

.0225 

142 

.224 

.0659 

1400 

3.788 

.0213 

152 

.245 

.0649 

1500 

3.993 

.0202 

162 

.265 

.0638 

1600 

4.196 

.0192 

172 

1.285 

.0628 

1700 

4.402 

.0183 

182 

1.306 

.0618 

1800 

4.605 

.0175 

192 

1.326 

.0609 

1900 

4.808 

.0168 

202 

1.347 

.0600 

2000 

5.012 

.0161 

212 

1.367 

.0591 

2100 

5.217 

.0153 

230 

1.404 

.0575 

2200 

5.420 

.0149 

250 

1.444 

.0559 

2300 

5.625 

.0142 

275 

1.495 

.0540 

2400 

5.827 

.0138 

300 

1.546 

.0522 

2500 

6.032 

.0133 

325 

1.597 

.0506 

2600 

6.236 

.0130 

350 

1.648 

.0490 

2700 

6.440 

.0125 

375 

1.689 

.0477 

2800 

6.644 

.0121 

400 

1.750 

.0461 

2900 

6.847 

.0118 

450 

1.852 

.0436 

3000 

7.051 

.0114 

TABLE   8. 

Temperature  of  the  Boiling  Point  at  Different  Heights  of  the 
Mercury  Column.f 


Inches    

29.92 

28.75 

27.62 

26.52 

25.46 

24.44 

23.45 

Temp.  F.  

212 

210 

208 

206 

204 

202 

200 

Inches    

Temp.  F.  :_„ 

22.50 
198 

21.58 
196 

20.68 
194 

19.83 
192 

19.00 
190 

18.20 

188 

17.42 
186 

*  Suplee's  M.  E.  Reference  Book. 
t  Smithsonian  Tables. 


412 


TABLE   9. 

Weight  of  Pure  Water  per  Cubic  Foot  at  Various 
Temperatures.* 


Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.  ft. 

B.  t.  u. 
per  pound 
above  32 

Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.  ft. 

B.  t.  u. 
per  pound 
above  32 

32 

62.42 

0.00 

77 

62.26 

45.04 

33 

62.42 

1.01 

78 

62.25 

46.04 

34 

62.42 

2.02 

79 

62.24 

47.04 

35 

62.42 

3.02 

80 

62.23 

•48.03 

36 

62.42 

4.03 

81 

62.22 

49.03 

37 

62.42 

5.04 

82 

62.21 

50.03 

38 

62.42 

6.04 

83 

62.20 

51.02 

39 

62.42 

7.05 

84 

62.19 

52.02 

40 

62.42 

8.05 

85 

62.18 

53.02 

41 

62.42 

9.05 

86 

62.17 

54.01 

42 

62.42 

10.06 

87 

62.16 

55.01 

43 

62.42 

11.06 

88 

62.15 

56.01 

44 

62.42 

12.06 

89 

62.14 

57.00 

45 

62.42 

13.07 

90 

62.13 

58.00 

46 

62.42 

14.07 

91 

62.12 

59.00 

47 

62.42 

15.07 

92 

62.11 

60.00 

48 

62.41 

16.07 

93 

62.10 

60.99 

49 

62.41 

17.08 

94 

62.09 

61.99 

50 

62.41 

18.08 

95 

62.08 

62.99 

51 

62.41 

19.08 

96 

62.07 

63.98 

52 

62.40 

20.08 

97 

62.06 

64.98 

53 

62.40 

21.08 

98 

62.05 

65.98 

54 

62.40 

22.08 

99 

62.03 

66.97 

55 

62.39 

23.08 

100 

62.02 

67.97 

56 

62.39 

24.08 

101 

62.01 

68.97 

57 

62.39 

25.08 

102 

62.00 

69.96  - 

58 

62.38 

26.08 

103 

61.99 

70.96 

59 

62.38 

27.08 

104 

61.97 

71.96 

60 

62.37 

28.08 

105 

61.96 

72.95 

61 

62.37 

29.08 

106 

61.95 

73.95 

62    ' 

62.36 

30.08 

107 

61.93 

74.95 

63 

62.36 

31.07 

108 

61.92 

75.95 

64 

62.35 

32.07 

109 

61.91 

76.94 

65 

62.34 

33.07 

.   110 

61.89 

77.94 

66 

62.34 

34.07 

111 

61.88 

78.94 

67 

62.33     • 

35.07 

112 

61.86 

79.93 

68 

62.33    - 

36.07 

113 

61.  85 

80.93 

69 

62.32 

37.06 

114 

61.83 

81.93 

70 

62.31 

38.06 

115 

61.82 

82.92 

71 

62.31 

39.06 

116 

61.80 

83.92 

72 

62.30 

40.05 

117 

61.78 

84.92 

73 

62.29 

41.05 

118 

61.77 

85.92 

74 

62.28 

42.05 

119 

61.75 

86.91 

75 

62.28 

43.05 

120 

61.74 

87.91 

76 

62.27 

44.04 

121 

61.72 

88.91 

Kent's  M.  E.  Pooket-Book.    8th  Edition. 
413 


Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.  ft. 

B.  t.  u. 

per  pound 
above  32 

Temp  . 

«-• 

Weight 
Ibs.  per 
cu.  ft. 

B.  t.  u. 
per  pound 
above  32 

122 

61.70 

89.91 

167 

60.83 

134.86 

128 

61.68 

90.90 

168 

60.81 

.   135.86 

124 

'  61.67 

91.90 

169 

60.79 

138.88 

125 

61.65 

92.90 

170 

60.77 

137.87 

126 

61.63 

93.90 

171 

60.75 

138.87 

127 

61.61 

94.89 

172 

60.73 

139.87 

128  . 

61.60 

95.89 

173 

60.70 

140.87 

129 

61.58 

96.89 

174 

60.68 

141.87 

130 

61.56 

97.89 

175 

60.66 

142.87 

131 

61.54 

QO     QO 

176 

60.64 

143.87 

132 

61.52 

99.88 

177 

60.62 

144.88 

133 

61.51 

100.88 

178 

60.59 

145.88 

134 

61.49 

101.88 

179 

60.57 

146.88 

135 

61.47 

102.88 

180 

60.55 

147.88 

136 

61.45 

103.88 

181 

60.53 

148.88 

137 

61.43 

104.87 

182 

60.50 

149.  a9 

138 

61.41 

105.87 

183 

60.48 

150.89 

139 

61.39 

106.87 

184 

60.46 

151.89 

140 

61.37 

107.87 

185 

60.44 

152.89 

141 

61.36 

108.87 

186 

60.41 

153.89 

142 

61.34 

109.87 

187 

60.39 

154.90 

143 

61.32 

110.87 

188 

60.37 

155.90 

144 

61.30 

111.87 

189 

60.34 

156.90 

145 

61.28 

112.86 

190 

60.32 

157.91 

146 

61.26 

113.86 

191 

60.29 

158.91 

147 

61.24 

114.86 

192 

60.27 

159.91 

148 

61.22 

115.86 

193 

60.25 

160.91 

149 

61.20 

116.86 

194 

60.22 

161.92 

150 

61.18 

117.86 

196 

60.20 

162.92 

151 

61.16 

118.86 

196 

60.17 

163.92 

152 

61.14 

119.86 

197 

60.15 

164.93 

153 

61.12 

120.86 

198 

60.12 

165.93 

154 

61.10 

121.86 

199 

60.10 

166.94 

155 

61.08 

122.86 

200 

60.07 

167.94 

156 

61.06 

.123.86 

201 

60.05 

168.94 

157 

61.04 

124.86 

202 

60.02 

169.95 

158 

61.02 

125.86 

203 

60.00 

170.95 

159 

61.00 

126.86 

204 

59.97 

171.96 

160 

60.98 

127.86 

205 

59.95 

172.96 

161 

60.96 

128.86 

206 

59.92 

173.97 

162 

60.94 

129.86 

207 

59.89 

174.97 

163 

60.92 

130.86 

208 

59.87 

175.98 

164 

60.90 

131.86 

209 

59.84 

176.98 

165 

60.87 

132.86 

210 

59.82 

177.99 

166 

60.85 

133.86 

211 

59.79 

178.99 

212 

59.76 

180. 

414 


TABLE   10. 
Boiling  Point  of  Water  at  Different  Heights  of  Vacuum. 


Temp. 
F. 

Height  of 
mercury  in 
vacuum  tube 
in  inches 

Temp. 
P. 

Height  of 
mercury  in 
vacuum  tube 
in  inches 

212.0 

0.00 

175.8 

16.00 

210.3 

1.00 

172.6 

17.00 

208.5 

2.00 

169.0 

18.00 

206.8 

3.00 

165.3 

19.00 

204.8 

4.00 

161.2 

20.00 

202.9 

5.00 

156.7 

21.00 

200.9 

6.00 

151.9 

22.00 

199.0 

7.00 

146.5 

23.00 

196.7 

8.00 

140.3 

24.00 

194.5 

9.00 

133.3 

25.00 

192.2 

10.00 

124.9 

26.00 

189.7 

11.00 

114.4 

27.00 

187.3 

12.00 

108.4 

28.00 

184.6 

13.00 

102.0 

29.00 

181.3 

14.00 

98.0 

29.92 

178.9 

15.00 

TABLE  11. 

Weight   of  Water   with   Air   per   Cubic   Foot   at   Different 
Temperatures  and  at  Saturation. 


fr 
A 

1 

£  « 

be  .2 

'53  cu 

£& 

fH 
ft 

5 
I 

£3  CD 

bfi.S 

'53   03 

£& 

fr 
ft 

1 

j5  ta 

ft*  .5 

'53  03 

jfca 

PH 
ft 

a 
g 

'.G  "2 

SUO.S 
'3  03 
£& 

£H 
ft 

1 

.c  M 

fc£.S 
'3  03 
£& 

f=H 
ft 

1 

is 

0,   03 

£& 

—20 

0.166 

2 

0.529 

!  24 

.483 

46 

3.539 

68 

7.480 

90 

14.790 

—19 

0.174 

3 

0.554 

25 

.551 

47 

3.667 

69 

7.726 

91 

15.234 

—18 

0.184 

4 

0.582 

26 

.623 

48 

3.800 

70 

7.980 

92 

15.689 

—17 

0.196 

5 

0.610 

27 

.697 

49 

3.936 

71 

8.240 

93 

16.155 

—16 

0.207 

6 

0.639 

28 

.773 

50 

4.076 

72 

8.508 

94 

16.634 

—15 

0.218 

7 

0.671 

29 

1.853 

51 

4.222 

73 

8.782 

95 

17.124 

—14 

0.231 

8 

0.704 

30 

1.935 

52 

4.372 

74 

9.066 

96 

17.626 

—13 

0.243 

9 

0.739 

31 

2.022 

53 

4.526 

75 

9.356 

97 

18.142 

—12 

0.257 

10 

0.776 

1  32 

2.113 

54 

4.685 

76 

9.655 

98 

18.671 

—11 

0.270 

11 

0.816 

33 

2.194 

55 

4.849 

77 

9.962 

99 

19.212 

—10 

0.285 

12 

0.856 

34 

2.279 

56 

5.016 

78 

10.277 

100 

19.766 

—  9 

0.300 

13 

0.898 

35 

2.366 

57 

5.191 

79 

10.601 

101 

20.335 

—  8 

0.316 

14 

0.941 

36 

2.457 

58 

5.370 

80 

10.934 

102 

21.017 

—  7 

0.332 

15 

0.986 

37 

2.550 

59 

5.555 

81 

11.275 

103 

21.514 

—  C 

0.350 

16 

1.032 

38 

2.646 

60 

5.745 

82 

11.626 

104 

22.125 

—  5 

0.370 

17 

.080 

39 

2.746 

61 

5.941 

83 

11.987 

105 

22.750 

—  4 

0.389 

18 

.128 

40 

2.849 

62 

6.142 

84 

12.356 

106 

23.392 

—  3 

0.411 

19 

.181 

41 

2.955  ' 

63 

6.349 

85 

12.736 

107 

24.048 

______     *> 

0.43* 

20 

.235 

42 

3.064 

64 

6.563 

86 

13.127  ' 

108 

24.720 

—  1 

0.457 

21 

.294 

43 

3.177 

65 

6.782 

87 

13.526 

109 

25.408 

0 

0.481 

22 

.355 

44 

3.294 

66 

7.009 

88 

13.937 

110 

26.112 

1 

0.505 

23 

.418 

45 

3.414 

67 

7.241 

89 

14.359 

415 


~ 


TABLE  13. 

Properties   of  Air  with  Moisture  under  Pressure   of   One 
Atmosphere.* 


ft 

$ 

Mixtures  of  air  saturated 

§ 

.~ 

H 

with  vapor 

S3 

^ 

'3 

.a 

Weight  of  cubic 

si 

g| 

bJ2 

.a 

.a 

foot  of  the 

V 

."£ 

'O  i—i 

*-<  ra  *-> 

mixture. 

8  § 

s 

a 

—  iH 

«w  £3 

o  •*•* 

"3    G    r* 

03  P 

c 

s 

a, 

if 

O'" 
4J  oa 

Si 

||3 

^ 

3 

B 

!+» 

03 

fc 

§1 

og 

°o| 

1 

«•§ 

"o    . 

+*  x 

(H 

s 

'3 

£| 

bfe 

1 

>>w 

03  "S 

£^ 

E-fil 

•w  ° 

"S 

03 

•0  ® 

0  p£M< 

^  S* 

ts 

•o  * 

*O  £ 

•2  ^ 

•2-2  c 

0-0 

"o  G 

•3  .a 

«M 

<M    OS 

HI'S  a 

"i  M 

1 

of 

|£ 

"i  P 

1'S  o 

if 

J3  n 

.SP  ° 

i| 

.2'* 

0  > 

•Bl 

S^- 

SI 

g 

s  ^ 

Ss        D. 

••r  ft 

•*•*  ^* 

S  3  § 

•°  o 

I 

II 

l« 

~ 

So 

^    !r« 

w  5  > 

la 

$> 

ei 

«•§ 

CS  03 
«  £ 

P  O 

O  ft.S 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

o 

.935 

.0864 

0.044 

29.877 

.0863 

.000079 

.086379 

.00092 

1092.40 

48.5 

12 

.960 

.0842 

0.074 

29.849 

.0840 

.000130 

.084130 

.00115 

646.10 

50.1 

22 

.98C 

.0824 

0.118 

29.803 

.0821 

.000202 

.082302 

.00245 

406.40 

51.1 

32 

1.000 

.0807 

0.181 

29.740 

.0802 

.000304 

.080504 

.00379 

263.81 

3289.0 

52.0 

42 

1.020 

.0791 

0.267 

29.654 

.0784 

.000440 

.•078840 

.00561 

178.18 

2252.0 

53.2 

52 

1.041 

.0766 

0.388 

29.533 

.0766 

.000627 

.077227 

.00819 

122.17 

1595.0 

54.0 

60 

1.057 

.0764 

0.522 

29.399 

.0751 

.000830 

.075252 

.01251 

92.27 

1227.0 

55.0 

62 

1.061 

.0761 

0.556 

29.365 

.0747 

.000881 

.075581 

.01179 

84.79 

1135.0 

55.2 

70 

1.078 

.0750 

0.754 

29.182 

.0731 

.001153 

.073509 

.01780 

64.59 

882.0 

56.2 

72 

1.082 

.0747 

0.785 

29.136 

.0727 

.001221 

.073921 

.01680 

59.54 

819.0 

56.3 

82 

1.102 

.0733 

1.092 

28.829 

.0706 

.001667 

.072267 

.02361 

42.35 

600.0 

57.2 

92 

1.122 

.0720 

1.501 

28.420 

.0684 

.002250 

.070717 

.03289 

30.40 

444.0 

58.4 

100 

1.139 

.0710 

1.929 

27.992 

.0664 

.002848 

.069261 

.04495 

23.66 

356.0 

59.1 

102 

1.143 

.0707 

2.036 

27.885 

.0659 

.002997 

.068897 

.04547 

21.98 

334.0 

50.5 

112 

1.163 

.0694 

2.731 

27.190 

.0631 

.003946 

.067042 

.06253 

15.99 

253.0 

60.6 

122 

1.184 

.0682 

3.621 

26.300 

.0599 

.005142 

.065046 

.08584 

11.65 

194.0 

61.7 

132 

1.204 

.((671 

4.752 

25.169 

.0564 

.006639 

.063039 

.11771 

8.49 

151.0 

62.5 

142 

1.224 

.0660 

6.165 

23.756 

.0524 

.008473 

.060873 

.16170 

6.18 

118.0 

63.7 

152 

1.245 

.0649 

7.930 

21.991 

.0477 

.010716 

.058416 

.22465 

4.45 

93.3 

64.  7 

162 

1.265 

.0638 

10.099 

19.822 

.0423 

.013415 

.055715 

.31713 

3.15 

74.5 

65.8 

172 

1.285 

.0628 

12.758 

17.163 

.0360 

.016682 

.052682 

.46338 

2.16 

*59.2 

66.9 

182 

1.306 

.0618 

15.960 

13.961 

.0288 

.020536 

.049336 

.71300 

1.402 

48.6 

68.0 

192 

1.326 

.0609 

19.828 

10.093 

.0205 

.025142 

.045642 

1.22643 

.815 

39.8 

69.0 

202 

1.347 

.0600 

24.450 

5.471 

.0109 

.030545 

.041445 

2.80230 

.357 

32.7 

70.0 

In- 

212 

1.367 

.0591 

29.921 

0.000 

.0000 

.036820 

.036820 

finite 

.000 

27.1 

71.1 

Carpenter's  H.  &  V.  B.  and  Sturtevant's  Mech.  Draft. 


TABLE   14. 
Dew-Points  of  Air  According  to  Its  Hygrometric   State.* 


Relative  moisture 

T6H1D. 

90% 

80% 

70% 

60% 

50% 

c. 

F. 

C. 

F. 

C. 

F. 

C. 

F. 

c. 

F. 

C. 

F. 

0 

32.0 

—  1.5 

29.3 

—  3.0 

26.6 

—  4.9 

23.2 

—  6.5 

20.3 

—  9.2 

15.4 

2 

35.6 

0.9 

33.6 

—  0.9 

30.4 

—  2.5 

27.5 

-  4.8 

23.4 

—  7.1 

19.2 

4 

39.2 

2.4 

36.3 

0.9 

33.6 

—  0.9 

30.4 

—  2.9 

26.8 

—  5.3 

22.5 

6 

42.8 

4.5 

40.1 

2.9 

37.2 

0.9 

33.6 

—  1.3 

29.7 

—  3.7 

25.3 

8 

46.4 

6.4 

43.5 

4.5 

40.1 

2.7 

36.9 

0.6 

33.1 

—  1.9 

28.6 

10 

50.0 

8.5 

47.3 

6.8 

44.2 

4.5 

40.1 

2.5 

36.5 

0.0 

32.0 

12 

53.6 

10.5 

50.9 

8.5 

47.3 

6.8 

44.2 

4.3 

39.7 

2.0 

35.6 

14 

57.2 

12.3 

54.1 

10.5 

50.9 

8.5 

47.3 

6.2 

43.2 

3.7 

38.7 

16 

60.8 

14.4 

57.9 

12.6 

54.7 

10.6 

50.9 

8.3 

46.9 

5.6 

42.1 

18 

64.4 

16.5 

61.7 

14.6 

58.3 

12.4 

54.3 

10.0 

50.0 

7.4 

45.3 

20 

68.0 

18.3 

64.9 

16.5 

61.7 

14.4 

57.9 

11.9 

53.4 

9.2 

48.6 

22 

71.6 

20.3 

68.5 

18.4 

65.1 

16.3 

61.3 

13.7 

56.7 

11.6 

52.8 

24 

75.2 

22.2 

72.1 

20.5 

68.9 

18.4 

65.1 

15.6 

60.0 

13.0 

55.4 

26 

78.8 

24.4 

75.9 

22.2 

72.1 

20.1 

68.2 

17.6 

63.6 

14.7 

58.5 

28 

82.4 

26.3 

79.3 

24.2 

75.6 

22.0 

71.6 

19.5 

67.1 

17.5 

63.5 

30 

86.0 

28.3 

82.9 

26  .3 

79.3 

23.9 

75.0 

21.5 

70.7 

18.3 

64.9 

^> 

*<! 

Bfrtjy 

a 

' 

!Sj 

in" 

"^ 

^.^ 

°5 
30g 

^ 

5^^ 

* 

"^ 

*  Bulletin  21,  Int.  Ass'n  of  Refrig. 

Psychrometric  Charts  Recent  Tests. 

In  recent  years  a  highly  technical  study  of  humidity 
and  its  control  has  been  made  by  Mr.  Willis  H.  Carrier.  Fig. 
A  shows,  merely  for  the  sake  of  comparison,  how  closely  his 

results  checked  the  earlier 
values  obtained  by  the  Gov- 
ernment Weather  Bureau.  The 
following  charts,  Figs.  B  and 
C,  summarize  the  results  of 
Mr.  Carrier's  experiments 
°"VBULO  Fig.  C  is  a  part  of  Fig.  B 

Fig-  A-  drawn   to   a  larger  scale. 

As  one  illustration  of  the  use  of  the  chart,  refer  to  Fig. 
C  with  air  at  40  degrees  and  40  per  cent,  humidity.  If  this 
air  be  heated  to  100  degrees  without  addition  of  moisture 
it  will  be  seen  by  interpolation  that  the  humidity  drops  to 
about  8  per  cent.  If  the  same  be  heated  to  100  degrees 
and  enough  moisture  be  added  to  keep  the  relative  humid- 
ity at  46  per  cent.,  then  the  absolute  humidity  changes  from 
15  grains  to  120  grains  per  pound  of  air.  These  figures 
may  be  reduced  to  grains  per  cubic  foot  by  dividing  by  the 
volume  per  pound  as  given  in  the  second  column  and  will 
be  found  to  check  closely  with  those  given  by  Fig.  7  and 
Table  9.  Almost  any  other  points  relating  to  changes  in 
volume,  humidity  and  contained  heat  may  be  easily  worked 
out  by  these  curves.  41g 


419 


TABLE  15. 
Fuel  Value  of  American 


Coal 
name  or  locality 

Fuel  value  per  pound 
of  coal 

B.  t.  u. 
calcu- 
lated 

B.  t.  u. 
by  calor- 
imeter 

Theoret- 
ical evap- 
oration 
inlbs. 
-  from  and 
at  212 
deg.  F. 

ARKANSAS. 
Spadra  Johnson  Co.  

14,420 

9,215 

13,560 
8,500 

14,020 
13,097 

14,391 
15,198 
9,326 

13,714 
13,414 

14,199 
12,300 

12,962 
14,200 

11,812 
11,756 

11,781 
9.035 
9,739 
13,123 

8,702 

9,890 
11,756 

13,104 
12,936 

9,450 
14,273 

14.90 
12.22 
12.17 
9.54 

14.04 
8.80 

12.19 
9.35 
10.09 
13.58 

14.50 
13.56 

9.01 

14.89 
16.76 
9.65 

10.24 
12.17 

14.20 
13.90 

14.70 
12.73 
13.46 
13.39 

9.78 
13.41 

14.71 
14.70 

Coal  Hill,  Johnson  Co. 

Huntington  Co.    

Lignite    _ 

COLORADO. 
Lignite    ._    _ 

Lignite,   slack  

ILLINOIS. 
Big  Muddy,  Jackson  Co.     

Colchester,    Slack  

Giliespie  Macoupin  Co. 

Mercer  Co. 

INDIANA. 
Block   

Cannel 

IOWA. 
Good  Cheer  

KENTUCKY. 
Caking    _- 

Cannel  _    _ 

Lignite 

MISSOURI. 
Bevier  Mines  

NEW  MEXICO. 
Coal 

OHIO. 
Briar  Hill,  Mahoning  Co. 

Hocking  Valley             _        - 

PENNSYLVANIA. 
Anthracite 

Anthracite,   pea 

Pittsburgh  (average)     -_  — 

Youghiogheney  

TEXAS. 
Fort  Worth 

Lignite    _      

WEST  VIRGINIA. 
Pocahontas 

New  River  _. 

Sturtevant's  "Mechanical  Draft. 


421 


TABLE   16. 
Capacities   of  Chimneys.* 


Inside 
diam- 
eter of 
lined 
flue, 
inches 

6 
7 
8 
9 
10 
12 
15 
18 

Maximum  sq.  ft.  of  cast  iron  radiating 
surface  and  B.  t.  u.  for  a  flue  of  the 
given  diameter  and  height 

25 
feet 
high 

36 
feet 
high 

49 
feet 
high 

64 
feet 
high 

81 
feet 
high 

100 
feet 
high 

Steam 

146 
243 

36500 

228 
379 
57000 

327 
544 
81750 

445 
742 
111250 

582 
969 
145500 

909 
1514 

227250 

1537 
2561 
384250 

2327 
3878 

581750 

175 
291 
43750 

273 
455 

68250 

392 
653 

98000 

534 

890 
133500 

.      698 
1163 
174500 

1090 
1817 

272500 

1844 
3073 
461000 

2792 
4653 
698000 

204 
340 
51000 

319 
531 
79750 

457 
762 
114250 

623 
1038 
155750 

814 
1357 
203500 

1272 

2120 
318000 

2151 
3586 
537750 

3257 
5429 
814250 

233 
388 

58250 

364 
607 
91000 

523 
871 
130750 

712 
1187 
178000 

930 
1551 
232500 

1454 
2423 
363500 

2458 
4098 
614500 

3722 
6204 
930500 

262 

437 
65500 

410 
683 
102500 

588 
980 
147000 

801 
1335 

200250 

1047 
1745 
261750 

1636 

2726 
409000 

2766 
4610 
691500 

4188 
6980 
1047000 

291 

485 
72750 

455 
758 
113750 

653 

1083 
163250 

890 
1483 

222500 

1163 
1938 
290750 

1817 
3028 
454250 

3073 
5122 
768250 

4653 
7755 
1163250 

Hot   water 

B.  t.  u.  _  

Steam   

Hot  water  
B.  t.  u. 

Steam 

Hot  water 

B.  t.  u  

Steam    

Hot  water  
B.    t.   u. 

Steam 

Hot  water  
B.  t.  u. 

Steam 

Hot  water        

B.  t.  u.  

Steam   

Hot  water 

B.  t.  u. 

Steam   

Hot  water  _  _  _. 

B.   t.   u.   

Radiation  is  calculated  at  250  B.  t.  u.  steam,  150  B.  t.  u.  water. 

TABLE  17. 
Excelsior  Double  Wall  Stack.f 


Sizes,  Inches 

Area 

Collar 

No 

Stack 

Nominal 

Inside 

Outside 

Sq.  In. 

Inches 

7 

4x11 

3x10 

35/8X10% 

30 

8  and  9 

8 

4x13 

3x12 

3%xl2% 

36 

8,  9  and  10 

9 

4x14 

3x13 

3%xl3% 

39 

9  and  10 

12 

6x13 

5x12 

5%xl2% 

60 

9  and  10 

The  Model  Boiler  Manual. 
t  Excelsior  Furnace  Co. 


422 


TABLE  18. 
Equalization  of  Smoke  Flues — Commercial  Sizes.* 


Inside 

Brick  flue 

Rectangular 

Outside 

diameter 

not  lined 

lined  flue 

iron 

lined  flue 

well  built 

outside  of  tile 

stack 

6 

8i/2x8V2 

8 

7 

8y2x8y2 

7x7 

9 

8 

8V2x8% 

8V2x8V2 

10 

9 

81/2X13 

8%xl3 

11 

10 

8i/2xl3 

8%xl3 

12 

12 

13x13 

13x13 

14 

15 

13x17 

13x18 

17 

18 

17x2iy2 

18x18 

20 

Round  flue  tile  lining  is  listed  by  its  inside  measurement. 
Rectangular  lining  by  outside  measurement. 


TABLE  19. 
Dimensions  of  Registers. 


Size  of 
opening, 
inches 

Nominal 
area  of 
opening, 
square 
inches 

Effective 
area  of 
opening, 
square 
inches 

Tin  box  size, 
inches 

Extreme 
dimensions  of 
register  face, 
inches 

6x  10 

60 

40 

6ft  x  10ft 

714x1114 

8  x  10 

80 

53 

8%  x  10% 

9%  x  11% 

8x12 

96 

64 

8%  x  12% 

9%  x  13% 

8  x  15 
9x12 
9x14 
10x12 
10x14 

120 
108 
126 
120 
140 

.80 
72 
84 
80 
93 

o  /$  X  15  /& 

914  x  1214 
914  x  1414 
1014  x  1214 
1014  x  1414 

9%  x  1614 

107/8  X  13% 
107/8  X  15% 

1HI  x  1311 
1111  x  15H 

10  x  16 

160 

107 

1014  X  161J 

1111  x  177/8 

12  x  15 

180 

120 

12%  x  15% 

U&  x  17 

12  X  19 

228 

152 

12%  x  19% 

14ftx21 

14x22 

308 

205 

14%  x  227/8 

1614  x  24% 

15  x  25 

375 

250 

15%  x  25% 

17%  x  27% 

16x20 
16x24 

320 
384 

213 
256 

167/8  x  207/8 
16T/8  x  247/s 

18ft  x  22ft 
18ft  x  26ft 

20x20 

400 

267 

2011  x  2011 

22%  x  22% 

20x24 

480 

320 

2011  x  2411 

22%  x  26% 

20  x  26 

'520 

347 

2011  x  2611 

22%  x  28% 

21x29 

609 

403 

2111  X  2911 

23%  x  31% 

27x27 

729 

486 

2711  x  2711 

29%  x  29% 

27x38 

1026 

684 

2711x3811    . 

29%  x  40% 

30x30 

900 

600 

3011  x  3011 

32%  x  32% 

Dimensions  of  different  makes  of  registers  vary  slightly.    The  above 
are  for  Tuttle  &  Bailey  manufacture. 
*  The  Model  Boiler  Manual. 


423 


TABLE  20. 

Capacities   of  Warm   Air  Furnaces  of  Ordinary   Constructioi 
in  Cubic  Feet  of  Space  Heated.* 


Divided  space 

Fire-pot 

Undivided  space 

+10° 

0° 

—10° 

Diarn. 

Area 

+10° 

0° 

—10° 

12000 

10000 

8000 

18  in. 

1.8'sq.  ft. 

17000 

14000 

12000 

14000 

12000 

10000 

20 

2.2 

22000 

17000 

14000 

17000 

14000 

12000 

22 

2.6 

26000 

22000 

17000 

22000 

18000 

14000 

24 

3.1 

30000 

26000 

22000 

26000 

22000 

18000 

26 

3.7 

35000 

30000 

26000 

30000 

26000 

22000 

28 

4.3 

40000 

35000 

30000 

35000 

30000 

26000 

30 

4.9 

50000 

40000 

35000 

TABLE  21. 
Capacities  of  Hot-Air  Pipes  and  Registers.! 


Cubic  feet 

Equivalent 

Equiv- 

of space 

Cubic  feet 

Cubic  feet 

Size  of 

area  in 

alent  in 

on  first 

on  second 

on  third 

register 

round  or 

square  or 

floor  same 

floor 

floor 

leader  pipe 

riser  pipe 

will  heat 

6x8 

6  in. 

4x8 

400 

450 

500 

8x8 

7    " 

4x10 

450 

500 

560 

8x10 

8    " 

4x10 

500 

850 

880 

8x12 

8    " 

4x11 

800 

1000 

1050 

9x12 

9    " 

4x12 

1050 

1250 

1320 

9x14 

9    " 

4x14 

1050 

1350 

1450 

10x12 

10  •" 

4x14 

1500 

1650 

1800 

10x14 

10    " 

6x10 

1800 

2000 

2200 

10x16 

10    " 

6x10 

1800 

2000 

2200 

12x14 

12    " 

6x12 

2200 

2300 

2500 

12x15 

12    " 

6x12 

2250 

2300 

2500 

12x17 

12    " 

6x14 

2300 

2600 

2800 

12x19 

12    " 

6x14 

2300 

2600 

2800 

14x18 

14    " 

6x16 

2800 

3000 

3200 

14x20 

14    " 

6x16 

2900 

3000 

3200 

14x22 

14    " 

8x16 

3000 

3200 

3400 

16x20 

16    " 

8x18 

3600 

4000 

4250 

16x24 

16    " 

8x18 

3700 

4000 

4250 

20X24 

18    " 

10x20 

4800 

5400 

5750 

20x26 

20    " 

10x24 

6000 

7000 

7450 

*  Federal  Furnace  League  Handbook, 
t  Kidder's  Arch,  and  B'ld'rs  Pocket-Book. 


TABLE  22. 
Air  Heating  Capacity  of  Warm  Air  Furnaces.* 


Total 

Fire-pot 

Casing 

cross  sec. 
area  of 

No.  and  size  of  heat  pipes  that 

heat 

may  be  supplied 

pipes 

Diam 

Area 

Diam. 

18  in. 

1.8  sq.  ft. 

30"-32" 

180  sq.  in. 

3-9"  or  4-8" 

20 

2.2 

34"-36" 

280      • 

2-10"  and  2-9"  or  3-9"  and  2-8" 

22 

2.6 

36"-40" 

360      ' 

3-10"  and  2-9"  or  4-9"  and  2-8" 

24 

3.1 

40"-44" 

470      ' 

3-10",  1-9"  and  2-8"  or  2-10"  and  5-8" 

26 

3.7 

44"-50" 

565      ' 

5-10"  and  3-9"  or  3-10",  4-9"  and  2-8" 

28 

4.3 

48"-56" 

650      ' 

2-12",  3-10"  and  3-9"  or  5-10",  3-9"  and  2-8" 

30 

4.9 

52"-60" 

730      ' 

3-12",  3-10"  and  3-*9"  or  "5-10",  5-9"  and  1-8" 

TABLE  23. 

Sectional   Area    (Square   Inches)    of    Vertical   Hot   Air   Flues, 
Natural  Draft,  Indirect   System.f 

Outside  temperature  50°  F.    Flue  temperature  90°  F. 


STEAM 

WATER 

Sq.  ft. 

cast  iron 

radiation 

'd 

S3 

T3 

S3 

£  >» 

43    >> 

s  >> 

'P  >> 

to  - 

•-$ 

11 

|| 

II 

E| 

11 

t-<  j_, 

M 

11 

PH   02 

Oto  50 

100 

75 

63 

60 

75 

63 

60 

60 

50         75 

150 

113 

94 

80 

113 

94 

80 

80 

75       100 

200 

150 

125 

100 

150 

125 

100 

100 

100       125 

250 

188 

156 

125 

188 

156 

125 

125 

125       150 

300 

225 

188 

150 

225 

188 

150 

150 

150       175 

350 

263 

219 

175 

263 

219 

175 

175 

175       200 

400 

300 

250 

200 

300 

250 

200 

200 

200       225 

450 

338 

281 

225 

338 

281 

225 

225 

225       250 

500 

375 

313 

250 

375 

313 

250 

250 

250       275 

550 

413 

344 

275 

413 

344 

275 

275 

275       300 

600 

450 

375 

300 

450 

375 

300 

300 

300       325 

650 

488 

406 

325 

488 

406 

325 

325 

325       350 

700 

525 

438 

350 

525 

438 

350 

350 

350       375 

750 

563  • 

469 

375 

563 

469 

375 

375 

375       400 

800 

600 

500 

400 

600 

500 

400 

400 

Velocity 

feet  per  sec. 

2% 

4% 

5% 

6V2 

iy2 

2% 

4 

4 

Effective  area 

of  register. 

1.00 

1.50 

1.83 

2.17 

1.00 

1.00 

1.33 

1.33 

Factor  for 

*  Federal  Furnace  League  Handbook. 
t  The  Model  Boiler  Manual. 


425 


TABLE  24. 
Sheet  Metal  Dimensions  and  Weights. 


Wt.  per  sq 

ft.  in  Ibs. 

Decimal 
gage 

Approximate 

millimeters 

Iron 
480  Ibs.  per 
cu.  ft. 

Steel 
489.6  Ibs.  per 
cu.  ft. 

U.  S.  Gage 
numbers 

0.002 

0.05 

0.08 

0.082 

0.004 

0.10 

0.16 

0.163 

0.006 

0.15 

0.24 

0.245 

38-39 

0.008 

0.20 

0.32 

0.326 

34-35 

0.010 

0.25 

0.40 

0.408 

32 

0.012 

0.30 

0.48 

0.490 

30-31 

0.014 

0.36 

0.56 

0.571 

29 

0.016 

0.41 

0.64 

0.653 

27-28 

0.018 

0.46 

0.72 

0.734 

26-27 

0.020 

0.51 

0.80 

0.816 

25-26 

0.022 

0.56 

0.88 

0.898 

25 

0.025 

0.64 

.00 

1.020 

24 

0.028 

0.71 

.12 

1.142 

23 

0.032 

0.81 

.28 

1.306 

21-22 

0.036 

0.91 

.  .44 

1.469 

20-21 

0.040 

1.02 

.60 

1.632 

19-20 

0.045 

1.14 

.80 

1.836 

18-19 

0.050 

1.27 

2.00 

2.040 

18 

0.055 

1.40 

2.20 

2.244 

17 

0.060 

1.52 

2.40 

2.448 

16-17 

0.065 

1.65 

2.60 

2.652 

15-16 

0.070 

1.78 

2.80 

2.856 

15 

0.075 

1.90 

3.00 

3.060 

14-15 

0.080 

2.03 

3.20 

3.264 

13-14 

0.085 

2.16 

3.40 

3.468 

13-14 

0.090 

2.28 

3.60 

3.672 

13-14 

0.096 

2.41 

3.80 

3.876 

12-13 

0.100 

2.54 

4.00 

4.080 

12-13 

0.110 

2.79 

4.40 

4.488 

12 

0.125 

3.18 

5.00 

5.100 

11 

0.135 

3.43 

5.40 

5.508 

10-11 

0.150 

3.81 

6.00 

6.120 

9-10 

0.165 

4.19 

6.60 

6.732 

8-9 

0.180 

4.57 

7.20 

7.344 

7-8 

0.200 

5.08 

8.00 

8.160 

6-7 

0.220 

5.59 

8.80 

8.976 

4-5 

0.240 

6.10 

9.60 

9.792 

3-4 

0.250 

6.35 

10.00 

10.200 

3 

For  weights  of  galvanized  iron,  multiply  weight,  black,  by:— 
No.  28         No.  28          No.  24          No.  22          No.  20         No.  18         No.  16 


1.25 


1.21 


1.16 


1.13 


1.11 


1.08 


1.07 


426 


TABLE  25. 


Weight   of   Round    Galvanized   Iron   Pipe   and   Elbows   of   the 
Proper  Gages  for  Heating  and  Ventilating  Work. 


Gage  and 
weight  per 
sq.  ft. 

"o 

i& 

Qft 

Ill 

53.9 

*.a 

Is 

Weight  per 
running 
foot 

Weight  of 
f  ull  elbow 

Gage  and 
weight  per 
sq.  ft. 

0 

is 

Q  ft 

«w  «j 

1'ft.l 
Oo.S 

O    . 
'cS«S 

Is 

Weight  per 
running 
foot 

Weight  of 
full  elbow 

No.  28 
0.78 

3 

4 
5 
6 

7 
8 

9.43 

12.57 
15.71 
18.85 
21.99 
25.13 

7.1 
12.6 
19.6 
28.3 
38.5 
50.3 

0.7 
.1 
.2 
.4 

.7 
.9 

0.4 
0.9 
1.2 
1.7 
2.3 
2.9 

No.  20 
1.66 

36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 

113.10 
116.24 
119.38 
122.52 
125.66 
128.81 
131.95 
135.09 
138.23 
141.37 
144.51 

1017.9 
1075.2 
1134.1 
1194.6 
1256.6 
1320.6 
1385.4 
1452.2 
1520.5 
1590.4 
1661.9 

17.2 
17.8 
18.2 
18.7 
19.1 
19.6 
20.1 
20.6 
21.0 
21.5 
22.0 

124.4 
131.4 
139.4 
146.0 
152.9 
160.7 
168.6 
176.7 
185.0 
193.4 
202.2 

No.  26 
0.91 

9 
10 
11 
12 
13 
14 

28.27 
31.42 
34.56 
37.70 
40.84 
43.98 

63.6 
78.5 
95.0 
113.1 
132.7 
153.9 

2.4 
2.7 
2.9 
3.2 
3.4 
3.7 

4.3 
5.3 
6.4 
7.6 
8.9 
10.4 

No.  18 
2.16 

47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
60 

147.65 
150.80 
153.94 
157.08 
160.22 
163.36 
166.50 
169.65 
172.79 
175.93 
179.07 
182.21 
185.35 
188.50 

29.2 
29.8 
30.4 
31.0 
31.6 
32.2 
33.0 
33.6 
34.4 
34.9 
35.6 
36.1 
36.7 
37.4 

274.3 
286.6 
298.8 
309.9 
322.5 
335.1 
349.7 
463.4 
377.2 
390.7 
405.1 
418.8 
433.1 
448.6 

No.  25 
1.03 

15 
16 
17 
18 
19 
20 

47.12 
50.27 
53.41 
56.55 
59.69 
62.83 

176.7 
201.1 
227.0 
254.5 
283.5 
314.2 

4.5 
4.7 
5.0 
5.3 
5.6 
6.0 

13.5 
15.1 
17.0 
19.1 
21.4 
23.9 

1734.9 
1809.6 
1885.7 
1963.5 
2042.8 
2123.7 
2206.2 
2290.2 
2375.8 
2463.0 
2551.8 
2642.1 
2734.0 
2827.4 

No.  24 
1.16 

21 
22 
23 
24 
25 
26 

65.97 
69.12 
72.26 
75.40 
78.54 
81.68 

346.4 
380.1 
415.5 
452.4 
490.9 
530.9 

7.0 
7.3 
7.7 
8.0 
8.3 
8.7 

29.6 
32.3 
35.6 
38.6 
41.7 
45.1 

No.  22 
1.41 

27 
28 
29 
30 
31 
32 
33 
34 
35 

84.82 
87.97 
91.11 
94.25 
97.39 
100.53 
103.67 
106.84 
109.96 

572.6 
615.7 
660.5 
706.9 
754.8 
804.3 
855.3 
907.9 
962.1 

10.9 
11.4 
11.8 
12.2 
12.6 
13.0 
13.5 
13.9 
14.3 

59.1 
64.2 
68.6 
73.4 
78.3 
83.4 
88.9 
94.3 
99.9 

No.  16 

61 

62 
63 
64 
66 
68 
70 
72 

191.64 
194.78 
197.92 
201.06 
207.34 
213.63 
219.91 
226.19 

2922.5 
3019.1 
3117.3 
3217.0 
3421.2 
3631.7 
3848.5 
4071.5 

46.7 
47.5 
48.3 
49.1 
50.5 
52.1 
53.6 
55.1 

569.7 
589.0 
608.6 
628.5 
666.6 
708.6 
750.4 
793.4 

427 


TABLE  26. 

Specific  Heats,  Coefficients  of  Expansion,  Coefficients  of  Trans- 
mission, and  Fusing-Points  of  Solids,  Liquids  or  Gases.1" 


SUBSTANCE 

Specific 
heats 

Coefficient 
of 
expansion 

Coefficient 
of  trans- 
mission 

Fusion 
points, 
degrees 

Antimony  

0.0508 

.00000602 

.00022 

815 

Copper  

0.0951 

.00000955 

.00404 

1949 

Gold 

0  0324 

00001060 

1947 

Wrought  iron 

0.1138 

.00000895 

00089 

2975 

Glass  _ 

0.1937 

.00000478 

.0000008 

1832 

Cast  iron  _ 

0.1298 

.00000618 

.000659 

2192 

Lead   

0.0314 

.00001580 

.00045 

621 

Platinum    

-     0.0324 

.00000530 

3452 

Silver    

0.0570 

.00001060 

.00610 

1751 

Tin 

0.0562 

.00001500 

00084 

446 

Steel  (soft) 

0.1165 

.00000600 

.00062 

2507 

Steel  (hard) 

0.1175 

.00000689 

.00034 

2507 

Nickel  steel  36%  

.00000003 

Zinc  

0.0956 

.00001633 

.00170 

787 

Brass   

0.0939 

.00001043 

.00142 

1859 

Ice 

0  5040 

.00000375 

.000024 

32 

Sulphur 

0.2026 

.00006413 

Charcoal  _ 

0.2410 

.00007860 

.000002 

Aluminum    

0.1970 

.00002313 

.00203 

1213 

Phosphorus  

0.1887 

.00012530 

Water 

1.0000 

.00008806 

.000008 

Mercury 

0.0333 

.00003333 

.00011 

Alcohol  (absolute) 

0.7000 

.00015151 

.000002 

Coeffi- 

Con- 

cient of 

stant 

Con- 

cubical 

pres- 

stant 

expansion 

sure 

volume 

atl 

atmos. 

Air 

0  93751 

0  16847 

003671 

0000015 

0  21751 

0  15507 

003674 

.0000012 

Hydrogen  _      

3.40900 

2.41226 

.003669 

.0000012 

Nitrogen  

0.24380 

0.17273 

.003668 

.0000012 

Superheated  steam 

0.4805 

0.346 

.003726 

Carbonic  acid 

0.2170 

0.1535 

.00000122 

*  Kent  and  Suplee. 


428 


TABLE  27. 

Pressure   in   Ounces,   per   Square   Inch,   Corresponding?   to 
Various  Heads  of  Water,  in  Inches.* 


Head 
in 
inches 

Decimal  parts  of  an  inch 

.0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

0 
1 
2 
3 
4 
5 
6 
7 
8 
9 

.06 
.63 
1.21 
1.79 
2.37 
,2.94 
3.52 
4.10 
4.67 
5.26 

.12 
.69 
1.27 
1.85 
2.42 
3.00 
3.58 
4.16 
4.73 
5.31 

.17 
.75 
1.33 
1.91 
2.48 
3.06 
3.64 
4.22 
4.79 
5.37 

.23 
.81 
1.39 
1.96 
2.54 
3.12 
3.70 
4.28 
4.85 
5.42 

.29 
.87 
1.44 
2.02 
2.60 
3.18 
3.75 
4.33 
4.91 
5.48 

.35 
.93 
1.50 
2.08 
2.66 
3.24 
3.81 
4.39 
4.97 
5.54 

.40 
.98 
1.56 
2.14 
2.72 
3.29 
3.87 
4.45 
5.03 
5.60 

.46 
1.04 
1.62 
2.19 
2.77 
3.35 
3.92 
4.50 
5.08 
5.66 

.52 
1.09 
1.67 
2.25 
2.83 
3.41 
3.98 
4.56 
5.14 
5.72 

.58 
1.16 
1.73 
2.31 

2.89 
3.47 
4.04 
4.62 
5.20 

TABLE  28. 

Height  of  Water  Column,  in  Inches,  Corresponding;  to  Pres- 
sures, in  Ounces,  per  Square  Inch.* 


Decimal  parts  of  an  ounce 


J.  1COOU1  C 

In  ounces 
per  square 
inch 

.0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

0 

.17 

.35 

.52 

.69 

.87 

1.04 

1.21 

1.38 

1.56 

1 

~:L73 

1.90 

2.08 

2.25 

2.42 

2.60 

2.77 

2.94 

3.11 

3.29 

2 

3.46 

3.63 

3.81 

3.98 

4.15 

4.33 

4.50 

4.67 

4.84 

5.01 

3 

5.19 

5.36 

5.54 

5.71 

5.88 

6.06 

6.23 

6.40 

6.57 

6.75 

4 

6.92 

7.09 

7.27 

7.44 

7.61 

7.79 

7.96 

8.13 

8.30 

8.48 

r 

8.65 

8.82 

9.00 

9.17 

9.34 

9.52 

9.69 

9.86 

10.03 

10.21 

6 

10.38 

10.55 

10.73 

10.90 

11.07 

11.26 

11.43 

11.60 

11.77 

11.95 

7 

12.11 

12.28 

12.46 

12.63 

12.80 

12.97 

13.15 

13.32 

13.49 

13.67 

8 

13.84 

14.01 

14.19 

14.36 

14.53 

14.71 

14.88 

15.05 

15.22 

15.40 

9 

15.57 

15.74 

15.92 

16.09 

16.26 

16.45 

16.62 

16.76 

16.96 

17.14 

Suplee's  M.  E.  Reference  Book. 


429 


4ooj  IBOUII  aad 

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430 


TABLE  30. 
Expansion  of  Wrought-Iron  Pipe  on  the  Application  of  Heat. 


Temp,  air 

when 

pipe 

is  fitted 


Increase  in  length  in  inches  per  100  feet 
when  heated  to 


Deg.  F. 

160 

180 

200 

212 

220 

228 

240 

274 

0 

1.28 

1.44 

1.60 

1.70 

1.76 

1.82 

1.92 

2.19 

32 

1.02 

1.18 

1.34 

1.44 

1.50 

1.57 

1.66 

1.94 

50 

.88 

1.04 

1.20 

1.30 

1.36 

1.42 

1.52 

1.79 

70 

.72 

.88 

1.04 

1.14 

1.20 

1.26 

1.36 

1.63 

TABLE  31. 
Tapping-  List  of  Direct  Radiators. t 

STEAM. 


ONE-PIPE  WORK 


TWO-PIPE  WORK 


Radiator  area 
square  feet 

Tapping  diam- 
eter —  inches 

Radiator  area 
square  feet 

Tapping  diam- 
eter—inches 

0—24 
24—60 
60  —  100 
100  and  above 

1 
1% 

1% 

2 

0—48 
48  —  96 
96  and  above 

1    x% 
l^xl 

i%xi% 

WATER. 
Tapped  for  supply  and  return. 


Radiator  area 
square  feet 

Tapping  diameter 
inches 

0  —  40 
40  —  72 
72  and  above 

1 
1% 

1% 

*  Holland  Heating  Manual, 
t  American  Radiator  Co. 


431 


TABLE  32. 
Pipe  Equalization.        (Sec  also  Table  21 


This  table  shows  the  relation  of  the  o  ^^^^^  e, 

combined    area    of    small   round   warm  w  i- I-H  I-H  ,J  ,-H  rn, 

air  ducts  or  pipes  to  the  area  of  one  "_;  _;,_;|_;2,-;  rn'! 


large  main  duct.  S^*-  ^f^^*^  °5®T1 

The  bold  figures  at  the  top  of  the  ^-j^ico  ^uttet-os  o,-,«o 

column  represent  the  diameters  of  '  «H«w«^Tio»floa'*-i  ei'wS 

the  small  pipes  or  ducts;  those  in 
the    left-hand    vertical    columns 
are  the   diameters  of  the  main 
pipes.     The  small  figures  show 


""*  I-H    i-i  r-i  rH  rH  I-H   I-H  (M  ~i  oi  ri 


COr-liM     CO  in  CO  00  35     rH  CO  •**  CO  00     C 

the  number  of  small  pipes  that  ^  ^  ^  *-  <-*  ^  ~  ~  oi  -M  ^  ~i  oi  w 

CM  —  -M  co   it  to  x  i  01   -ri~  >^  C-.T*   "# 

each   mam  duct  will  supply.  «  _  ^  ^  _•  _•  ^  ,,;,.;  ~;  ~;  ~;  ,.;  co"  ci 

Example.—  To  supply  sixteen  j^^'^  *-.'=•'-'.*}**  *:<»<=><»«  *: 

10-inch  pipes:    Refer  to  column 

having    10    at    top;     follow  o  rHto^ei-  o-.  i-  to  it  to  oNitst-o  K 

down    to    small    figure    16,  ^  ^  ^'  ^  ^  ^  -'  <M'  ~i  -i  ^i  «  cc  ^  ^  -t' 

thence  left   on   the  hori- 
zontal  line  of  the  bold-  * 

face     figure     in     the  *» 

outside  column,  and  *~  ' 

we  find  that  one  "-  ~! 

30-inch  main  will 

supply  air  for  <e  «•]  M  in  i>-  o^i^csrH  •*«0'-;*i;i^  ~  !--_,._-  -^  -.  - 

the  sixteen  ^  x>>o^«9»-  t-  1^  s. 

10  -  inch  m  w  ^j  o  oo  r-i  Wfflooe^iia   ocooowt^.  i-iioi-iic^t  01  co  o 


CM  <N  1C  QO    tH  •*  00  o-l  <O    r-<  in  O  Jt--  'd     Ol  ift  CC  T-I  Oi    O  1-1  'M  re  -~    "^  -^  X 


»H  TH  <M   c<  <M  co  eo  •*   10  in  co  t^  0     0 


COCDCiCOOO    NQOMOJt^    CO  (MOO  050    r-i  *J  M  -t<  to 
^r^tMftJeq    CO  CO  "*  w  1(5    CO  t^  J^  00  ^ 


,^22  ^SSS2  2SS""  s-*^^  fes^jsg  §^^gg  ssg 


irtl>O5coO5    i-iooOOOO    ^ItO05(Mi-5    OS  W 
^^^0605-     *H-H^^«     ^l^^COf?     00 


co  j>.co<M?o 

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co   in  oo  S  rt  i-r  ?i?f  TH  «  «  S  «  S  M  «5  w  *  ?*  * 


N<M<»     i-lODb-Ss5^  SODSSLO(?''1  '"QpOcOCO  Ot^iftO-*  OOOOO 

CO  -*  m    t-  «5  C    -  i  i  -  /    =    rt  J-   —  -t-   ~   -^   ~   -r  -  J-  -M   *    ~  (?1  1-  "*  O 

i—  *  T—  t  i—  I  i-H  C^  Ol  C>-1    M  CO  CO  -*  ~^<  If3  tO  SO  J^-  OO  00  Ct  O  T-H  <7>} 

O^t^   (M^cof^co  ®  b-  m  o  in  moioo*  mgooo®  N  1-1  •*  in  m   it 

(M  00  TJ<  rH    o  Q  ^  TC  i^  01  C:  t^  00  1^  X  j-  -M  r   -c  ~  :  co  5  -f  r;  T—  ro  i-  t^  J--    :•? 

iHi-i<MCo   ^inoi^oo  o  >-i  co  m  i>  S  c$  &  do  p  4t  t-  i  --  t-oo  cccir-^o  t^ 

IH  r-i  i-t  I-H  r-i  rHj  cj  c3  SJ  w  coco-*-*-*  mmto25i^-  jt^ 


^  ^  «  ;£  »   CB  r-  «  »  O   ^  c,  «  ^  uj   jo  ^  oo  g  O    ~  %  <o  *  «    «o  g  „ 
432 


TABLE   33. 

Sizes  of  Hot-Water  Mains. 
Open   Tank    System. 

Assumed  Length  100  feet.f 


Capacity,  square  feet  of  direct  radiation 

JMoG  (3  in  in 

inches 

Two-pipe* 

One-pipe 

Attic 

up  feed 

up  feed 

main 

1% 

100 

50 

150 

1% 

150 

75 

225 

2 

275 

125    ' 

375 

2% 

375 

2-25 

540 

3 

600 

400 

900 

3% 

800 

500 

1300 

4 

1100 

700 

1800 

g 

1900 

1200 

3200 

6 

3000 

2000 

5000 

7 

4500 

3000 

7200 

8 

6000 

4000 

10000 

For  mains  over  100'  reduce  capacity  in  the  ratio  of 


100 


length 

*  Mains  for  indirect  radiation  should   have  a   rated  capacity  ap- 
proximating 66  per  cent,  of  the  values  in  this  column. 


TABLE   34. 

Sizes  of  Hot- Water  Branches  and  Risers. 
Open  Tank  System. 


Pipe 

diaii!. 
inches 

Up  Feed 

Down  feed 
from  attic 
not  exceeding 
four  floors 

First 
Floor 

Second 
Floor 

Third 
Floor 

75 
130 
190 
350 
510 
700 

Fourth 
Floor 

1 
1% 

1% 

2 

2% 

.      3 

50 
'90 
125 
225 
325 
500 

65 
110 
160 
300 
425 
600 

85 
145 
215 

375 

580 
800 

75 
125 

200 
350 
600 
900 

Take  first  floor  supply  branches  from  top  of  main.    Risers  above  first 
floor  at  45°. 

TABLE  35. 

Hot-Water  Radiator  Tapping's. 
Open  Tank  System. 


Size  of  Radiator 


Up  to  40  sq.  ft. 

40  to  72  sq.  ft. 

Above  72  sq.  ft. 


Supply  and  Return 


1x1 

x  114 
x  iy2 


433 


TABLE  36. 
Honeywell  System.     Pipe  Sizes. 

The   area  of  the  main  must   equal   or   exceed   slightly   the 
combined  area  of  the  valves  it  is  to  supply. 


Riser  Sizes  and  Square  Feet  of  Radiation. 


Pipe  size,  inches 

First  Floor 

Second  Floor 

Third  Floor 

tt 

% 

Up  to    30 

30  to    60 
60  to  100 

Up  to    40 
40  to  100 
Over  100 

Up  to    50 
50  to  125 
Over  125 

The  valve  on  the  radiator  at  the  end  of  the  main  should  generally  be 
made  one  size  larger  than  the  list. 

TABLE  37. 

Gravity  Hot- Water  Heating.     Approximate  Capacities  of 
Mains  and  Risers  for  Range  from  180  to  ISO  Deg.  Fahr.$ 

Capacities  (including  losses  in  transit)  are  in  1000  B.  t.  u.  per  hour 
and  allow  for  average  resistance  of  boilers,  radiators  and  piping.  For 
sq.  ft.  of  radiating  surface  supplied  (160  B.  t.  u.  per  sq.  ft.),  multiply 
the  tabular  figures  by  6.25. 

MAINS. 


* 

Diameter  of  main,  in. 

fil 

S3 

-M" 

-C-P 

£8 

W«H 

1V4 

"1% 

2 

2% 

3 

3% 

4 

4% 

5 

6 

7 

8 

H 

w 

Capacity  in  1000  B.  t.  u. 

100 

7 

15 

22 

40 

60 

98 

133 

188 

240 

315 

480 

675 

900 

200 

8 

12.5 

18 

32 

50 

82 

114 

157 

206 

270 

415 

590 

800 

300 

9 

11 

16 

29 

45 

75 

106 

144 

190 

250 

385 

550 

740 

400 

10 

10 

15 

27 

42 

70 

100 

135 

180 

238 

367 

520 

700 

RISERS. 


Diameter  of  riser,  in. 

Diameter  of  riser,  in. 

II 

% 

1 

i* 

1% 

2 

2% 

£•8 

•a« 

% 

% 

1 

1% 

1% 

2 

a 

H 

Capacity  in  1000  B.  t.  u. 

Capacity  in  1000  B.  t.  u. 

10 

4.0 

7.5 

15.0 

22.0 

42 

67 

30 

3.4 

7.1 

13.1 

26 

38 

74 

15 

5.0 

9.2 

18.7 

27.4 

52 

82 

40 

4.0 

8.2 

15.2 

31 

45 

86 

20 

5,8 

10,6 

21.7 

31.8 

60 

95 

50 

4.5 

9.2 

17.0 

35 

51 

97 

25 

6.4 

11.8 

24.2 

35.5 

67 

106 

60 

4.9 

10.1 

18.5 

38 

56 

107 

*  The  length  and  mean  height  above  boiler  are  those  of  the  circuit  for 
the  most  distant  radiator  in  lowest  location. 

t  The  mean  height  above  boiler  is  that  of  the  circuit  in  question.  This 
table  is  for  a  circuit  200  ft.  long.  For  other  lengths  allow  about  in  pro- 
portion as  given  above  for  mains. 

J  Marks— M.  E.  Handbook. 

434 


I 

£ 

a 

C 

S 

4) 
*1 

H    « 

g  8 


1^ 
sg 


. 
•ss 

Sft 


j-j  -1-1 

.22  S1 


M 


9  as 
!  Pi 


8 

i—f          ITS  ' 


An-rt' 

S3 


oS& 
ft  ft  AH 


II 


II 


iSSS8^5ij-'S'lftft€ 

JIM-*,: 
_  >> 


PH 


435 


saqoui 
ni  - 


i-H  T-H  C^l 


co  oo  in  ?O  I-H  co  O 


TIf  -UIBIQ 


1 

iis«afi$i 

I 

i-H  rH  I-H  r-H  I-H  frl 

rH 

1 

I-H 

881111111 

! 

88I11II1S 

§ 

I 

l 

I 

I 

lllililil 

I 

1 

1 

I 

8 
ni 

I(T 

rH 

436 


TABLE  40. 
Sizes  for  Steam  Supply  and  Return  lanes.t 


Pipe  Sizes 

Vz 

% 

1 

50 

1% 

100 
50 

300 
3800 
1500 

1% 

175 

100 

900 
6000 
3000 

2 

350 

200 

2000 
13000 
6000 

2% 

600 
300 

3800 
23000 
10000 

3 

3% 

1500 
700 

10000 
55000 

30000 

Supply  mains,  all  systems; 
downfeed  risers,  all  systems 

1000 
500 

6000 
37000 
18000 

Upfeed  risers,  one-pipe  system 

Dry  return  lines,  two-pipe  and 
vapor  systems  __    

50 

150 
2000 
800 

Wet  return  lines    

Vacuum  return  lines  

100 

400 

Pipe  Sizes 

4 

5 

6 

8 

10 

12 

14 

16 

Supply  mains,  all  systems; 
downfeed  risers,   all  systems.. 
Upfeed  risers,*  one-pipe  system 
Dry  return  lines,  two-pipe  and 
vapor  systems 

2000 
800 

13000 
78000 

3800 
1300 

23000 

6000 
1800 

37000 

13000 
3000 

78000 

23000 

35000 

55000 

78000 

Wet  return  lines 

Vacuum  return  lines  __ 

40000 

<;:>ooo 

Which  carry  condensation  from  radiators. 

TABLE  41. 
Sizes  of  Radiator  Connections.! 


One-pipe  radiators 

Two-pipe  radiators 

Size  of 
Radiator, 
square  feet 

Radiator 
connec- 
tion 

Hori- 
zontal 
branch 

Size  of 
Radiator, 
square  feet 

Size  of 
supply  con- 
nection 

Size  of 
return  con- 
nection 

20 
24 
40 
60 
80 
100 
200 

1 
1 

v& 

1% 
1% 
1% 
2 

1 
34 
1% 

1% 

t* 

2 

48 
96 
over  96 

1 
1% 
1% 

% 
1 

iy4 

t  Allen  and  Walker. 


437 


TABLE  42. 
Loss  of  Head  by  Friction  of  Pipes.* 

Loss  of  head  by  friction  in  each  100  feet  in  length  of  different  diameters  of  pipe  wh 
discharging  the  following  quantities  of  water  per  minute. 

INSIDE  DIAMETER  OF  PIPE  IN  INCHES 

00 
»s 

aad  ^eaj  biqno 

CsOOt-0 

r, 

QC 

— 

s 

H 

lllSg§ 

*  Dayton  Hydraulic  Co.  Catalog. 

188J  Ul 

p«aq  jo  ssoq; 

!§§$S8 

2  ij  S  rH  S  S 

rH^N<N 

a^nuiiu 
jad  cjaaj  biqno 

issiii 

ssiiis 

peaq  jo  s'soi 

ii^^ 

^sliss 

r-  1 

jad  ^aaj  biqno 

l>  rH  1ft  C5  C<1  <£> 

Sg5l5:il 

laajUl 

pBaq  jo  ssoi 

'  r-<  N  frq  M 

S8S613 

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jsd  ^aaj  oiqno 

CO  Ifl  t^  OS  TH  (M 

praaq  jo  ssoi 

CS  rH  G^l  CO  ^ 

a^nuiui 
jad  ^88j  biqno 

!§i^i 

praaq  jo  ssoi 

l^ssse 

SiSi^ig 

rH^M^lft 

— 
— 

rHrHrH 

e^nuitn 
iad  ^aaj  oiqno 

SSSS^to 

e<) 

S  5  ^  rH  10  O 

inOOrH  -*J>0 
rH  rH  1—*  C<l 

^aaj  ui 
pB8q  jo  ssoi 

gg*2S^g 

rHN^W^ 

o 

rH  rH  (M 

jad  ^aaj  biqno 

N  05  1ft  tO  t>  CS 

gsgin 

pBaq  jo  ssoi 

g^SrnS^ 

SISscs 

rH  <M  ^  0  00  rH 

r. 

rH   r-i  (>! 

e^nuini 

§S^^ 

CO  OS  5O  jy  OS  IO 

in  t~  o  fs  ift  oo 

^88J  UI 

pBaq  jo  ssoq; 

C-5  Tii  00  C<J  1-^  N 

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o  o  o  o  o  o 

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438 


TABLE  43. 

Comparative   Sizes  of  Steam  Mains  and  Returns  for  Gravity 
and  Mechanical  Vacuum   Systems. 


Size  of 
supply 
pipe 

Size  of  return 

Size  of 
supply 
pipe 

Size  of  return 

Gravity    I   Vacuum 

Gravity 

Vacuum 

% 

% 

y2 

4 

2% 

iy2 

1 

% 

% 

4% 

1% 

1% 

1 

i^ 

5 

3 

2 

1% 

1*4-* 

% 

6 

3% 

2% 

2 

1% 

% 

8 

4% 

3% 

2% 

2 

i 

10 

6 

4 

3 

2 

1-/4 

12 

6 

4% 

3V2 

2% 

11/4 

14 

7 

5 

Note.— For  short  runs  of  piping  where  the  friction  is  not  a  serious 
matter  the  above  table  will  work  out  satisfactorily.  These  sizes  are 
only  approximate  and  should  be  used  with  caution. 


TABLE   44. 
Expansion  Tanks — Dimensions  and  Capacities.* 


Size  in  inches 

Capacity  gallons 

Sq.  ft.  of  radiation 

9x20 

5y2 

150 

10x20 

8 

250 

12x20 

10 

350 

12x24 

12 

450 

12x30 

15 

550 

12x36 

18 

650 

14x30 

20 

700 

14x30 

24 

850 

16x30 

26  ' 

000 

16x36 

32 

1250 

10x48 

42 

1750 

18x60 

66 

2750 

20x60 

82 

4500 

22x60 

-100 

6000 

24x60 

122 

7500 

*  The  Model  Boiler  Manual. 


439 


TABLE   45. 
of  Flanged  Fitting*. 


All  fittings  and 
flanges 


m 


90° 
elbow 


45° 
elbow 


BE 


Long 
turn 
elbow 


Tee 


0. 


Cross 


Lateral 


ace 
C" 


ter 
rt  e 


10 
12 
14 
16 
20 
24  32 


7% 
9% 
11% 
14V4 
17 
18% 
21V* 
25 

21)1/2 


6 

7 

7% 
7% 
8 

9i/2 
11 


12 

14 

17V2 

20% 

24 

27 

30 

35 

40% 


61/2 


TABLE   46. 
Dimensions  of  Ells  and  Tees  for  Wrought  Iron  Pipe. 


Size 

E 

R 

D 

d 

t 

L 

T 

Vs 

% 

ft 

it 

ft 

ft 

i-y4 

% 

V4 

% 

% 

% 

-/v, 

i-y2 

% 

% 

7/8 

% 

:-V8 

7/8 

^4 

i-% 

7/8 

y2 

1-H 

% 

-% 

1-ft 

% 

2-!/4 

i-y8 

% 

i-% 

1-& 

-ft 

1-T5S 

ft 

2-% 

i-% 

i- 

i-ft 

1-% 

-7/8 

1-% 

3-Vs 

i-ft 

i-% 

l-7/8 

1-1/2 

2-% 

2_ 

ft 

3-% 

l-7/8 

i-% 

2- 

1-% 

2-% 

2-^4 

% 

4- 

2- 

2_ 

2-% 

2-1/s 

3-% 

2-7/8 

% 

4-% 

2-% 

2-% 

2-% 

2-% 

4- 

3-% 

% 

5-% 

2-% 

3- 

3-% 

2-% 

4-% 

4- 

7/8 

6-% 

3-% 

3-% 

3-% 

3-1/8 

5-y4 

4-% 

7/8 

7-% 

3-% 

4- 

4- 

3-% 

5-y8 

5-^4 

1- 

8- 

4- 

4-% 

4-% 

4- 

6-% 

6- 

1- 

8-% 

4-% 

5- 

4-% 

4r-Vs 

6-% 

6-y8 

1-% 

9-% 

4-% 

6- 

5-14 

4-% 

8-% 

7-7/8 

1-Vs 

11- 

5-1/2 

440 


TABLE   47. 

Loss    of    Pressure    in    Pipes    100    Feet    Long    in    Ounces    per 
Square  Inch  when  Delivering  Air  at  the  Velocities  Given. 


3J 

Diameter  of  pipe  in  inches 

gs 

1 

2 

3 

4 

6 

8 

10 

-12 

14 

16 

18 

300 

400 

0.100 
0.178 

0.050 
0.088 

0.033 
0.059 

0.025 
0.044 

0.017 
0.030 

0.012 
0.022 

0.010 
0.018 

0.008 
0.015 

0.007 
0.013 

0.006 
0.011 

0.006 
0.010 

600 

0.400 

0.200 

0.133 

0.100 

0.067 

0.050 

0.040 

0.033 

0.029 

0.025 

0.022 

800 

0.711 

0.356 

0.237 

0.178 

0.119 

0.089 

0.071 

0.059 

0.051 

0.044 

0.040 

1000 

1.111 

0.556 

0.370 

0.278 

0.185 

0.139 

0.111 

0.092 

0.079 

0.069 

0.062 

1200 

1.600 

0.800 

0.533 

0.400 

0.267 

0.200 

0.160 

0.133 

0.114 

0.100 

0.089 

1500 

2.500 

1.250 

0.833 

0.625 

0.417 

0.312 

0.250 

0.208 

0.179 

0.156 

0.139 

1800 

3.600 

1.800 

1.200 

0.900 

0.600 

0.450 

0.360 

0.300 

0.257 

0.225 

0.200 

2400 

6.400 

3.200 

2.133 

1.600 

1.067 

0.800 

0.640 

0.533 

0.457 

0.400 

0.356 

20 

24 

28 

32 

36 

40 

44 

48 

52 

56 

60 

300 

0.005 

0.004 

0.004 

0.003 

0.003 

0.002 

0.002 

0.002 

0.002 

0.002 

0.002 

400 

0.009 

0.007 

0.006 

0.006 

0.005 

0.004 

0.004 

0.004 

0.003 

0.003 

0.003 

600 

0.020 

0.017 

0.014 

0.012 

0.011 

0.010 

0.009 

0.008 

0.008 

0.007 

0.007 

800 

0.036 

0.029 

0.025 

0.022 

0.020 

0.018 

0.016 

0.015 

0.014 

0.013 

0.012 

1000 

0.056 

0.046 

0.040 

0.035 

0.031 

0.028 

0.025 

0.023 

0.021 

0.020 

0.019 

1200 

0.080 

0.067 

0.057 

0.050 

0.044 

0.040 

0.036 

0.033 

0.031 

0.029 

0.027 

1500 

0.125 

0.104 

0.089 

0.078 

0.069 

0.062 

0.057 

0.052 

0.048 

0.045 

0.042 

1800 

0.180 

0.167 

0.129 

0.112 

0.100 

0.090 

0.082 

0.075 

0.069 

0.064 

0.060 

2400 

0.320 

0.313 

0.239 

0.200 

0.17S 

0.160 

0.145 

0.133 

0.123 

0.119 

0.107 

Diagrams  for  Pipe  Sizes  and  Friction  Heads. 

To  illustrate  the  use  of  the  two  following"  diagrams,  ap- 
ply to  the  pipe  line,  B,  C,  Art.  147.  First,  let  I  =  1500  feet, 
(I  =  8  inches  and  v  '=  5  feet  per  second.  Trace  along-  the 
velocity  line  until  it  intersects  the  diameter  line,  then  fol- 
low the  ordinate  to  the  top  of  the  page  and  find  the  friction 
head,  13  feet  for  1000  foot  run  or  19.5  feet  for  the  1500  foot 
run.  Second,  let  Q  =  1.75  cubic  feet  per  second  and  d  =  8 
inches.  Trace  to  the  left  along  the  horizontal  line  represent- 
ing- the  volume  of  1.75  cubic  feet  until  it  intersects  the 
diameter  line,  then  read  up  and  find  the  same  friction  head 
as  before.  Third,  let  the  allowable  friction  head  for  1500 
feet  of  main  be  19  feet,  when  Q  =  1.75  cubic  feet  per  second 
or  when  v  =  5  feet  per  second.  Reverse  the  process  given 
above  and  find  an  8  inch  pipe. 


442 


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443 


TABLE   48. 
Temperature*    for   Tenting:    Direct    Steam    Radiation    Plants.* 


1 

m 

Test 
condi- 

Steam 
Tern- 

Steam  pressure  intended  for  zero  weather 

tion 

pcrji- 

ture 

Olb. 

lib. 

21b. 

31b. 

41b. 

51b. 

Olb. 

71b. 

81b. 

91b. 

10  lb. 

10  in. 

192.0 

63.3 

62.3 

9  " 

194.5 

64.2 

63.2 

62.3 

8  " 

197.0 

65.0 

64.0 

63.0 

62.2 

7  " 

199.0 

65.6 

64.7 

63.7 

62.8 

62.0 

6  " 

201.0 

66.3 

65.3 

64.3 

63.4 

62.6 

62.0 

5   " 

203.0 

67.0 

66.0 

65.0 

64.0 

63.3 

62.6 

61.9 

4   " 

205.0 

67.6 

66.6 

65.6 

64.7 

63.9 

63.2 

62.5 

61.7 

3   " 

207.0 

68.3 

67.2 

66.2 

65.3 

64.5 

63.8 

63.1 

62.3 

61.7 

2   " 

208.5 

68.8 

67.7 

66.7 

65.7 

65.0 

64.2 

63.6 

62.8 

62.0 

61.5 

1    " 

210.5 

69.4 

68.3 

67.5 

66.4 

65.6 

64.8 

64.2 

63.3 

62.6 

62.1 

61.5 

0  lb 

212.0 

70.0 

68.8 

67.8 

66.9 

66.1 

65.3 

64.6 

63.8 

63.1 

62.6 

6?  0 

l  " 

215.5 

71.2 

70.0 

69.0 

68.0 

67.2 

66.3 

65.8 

65.0 

64.2 

63.7 

63.0 

2   " 

218.7 

72.1 

71.0 

70.0 

69.2 

68.2 

67.3 

66.7 

65.9 

65.1 

64.5 

64.0 

3  " 

221.7 

72.0 

71.0 

70.0 

69.2 

68.3 

67.6 

66.7 

66.0 

65.4 

64.8 

4   " 

224.5 

71.8 

70.8 

70.0 

69.2 

68.4 

67.5 

66.7 

66.2 

65.7 

5  " 

227.2 

71.7 

70.8 

70.0 

69.2 

68.3 

67.6 

67.0 

66.3 

6  " 

229.8 

71.7 

70.8 

70.0 

69.2 

68.4 

67.7 

67.2 

7  " 

232.4 

71.7 

70.8 

70.0 

69.2 

68.6 

68.0 

8  " 

234.9 

71.7 

70.8 

70.0 

69.3 

68.7 

9  " 

237.3 

71.5 

70.5 

70.0 

69.3 

10   " 

239.4 

71.3 

70.7 

70.0 

Factors 

.670 

.675 

.678 

.684 

.688 

.692 

.694 

.698 

.702 

.705 

.707 

The  temperatures  in  this  table  are  for  a  plant  designed  for  0°  and  70°. 

Example. — It  is  desired  to  test  a  plant  designed  for  5  pounds  gage 
pressure  on  a  day  when  the  outside  temperature  is  22  degrees.  What 
should  be  the  temperature  in  the  rooms  with  steam  at  3  pounds  gage 
pressure?  It  will  be  noted  in  the  vertical  column  marked  5  pounds  that 
opposite  the  3  pound  pressure  68.3  degrees  may  be  expected  on  a  zero 
day.  As  the  temperature  was  22  degrees  above  we  must  add  22  times 
.692,  or  15.2  degrees,  thus  making  a  total  of  83.5  degrees,  the  tempera- 
ture which  should  exist  indoors. 

*  W.  W.  Macon. 


444 


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water 


Capaci 
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§    '5 a  !^"  .,  &  -.-g-S 

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Diameter 
Length  o 


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Note.— 
by  100  and  w 
Smokeless  bo 
the  manufa 


TABLE    50. 

Percentage  of  Heat  Transmitted  by  Various  Pipe-Coverings, 

From  Tests  Made  at  Sibley  College,  Cornell  University, 

and  at  Michigan  University.* 

Relative  amount 
Kind  of  covering  of  heat 

transmitted 

Naked  Pipe  100. 

Two  layers  asbestos  paper,  1  in.  hair  felt,  and  canvas 

cover  15.2 

Two  layers  asbestos  paper,  1  in.  hair  felt,  canvas  cover 

wrapped  with  manilla  paper  15. 

Two  layers  asbestos  paper,  1  in.  hair  felt 17. 

Hair  felt  sectional  covering-,  asbestos  lined 18.6 

One  thickness  asbestos  board  59.4 

Four  thicknesses  asbestos  paper  50.3 

Two  layers  asbestos  paper  77.7 

Wool  felt,  asbestos  lined  '. 23.1 

Wool  felt  with  air  spaces,  asbestos  lined 19.7 

Wool  felt,  plaster  paris  lined  25.9 

Asbestos  molded,  mixed  with  plaster  paris 31.8 

Asbestos  felted,  pure  long-  fibre    20.1 

Asbestos  and  sponge  18.8 

Asbestos  and  wool  felt  20.8 

Magnesia,  molded,  applied  in  plastic  condition 22.4 

Magnesia,   sectional  18.8 

Mineral  wool,  sectional  19.3 

Rock  wool,  fibrous  20.3 

Rock  wool,  felted  20.9 

Fossil  meal,  molded,  %   inch  thick  29.7 

Pipe  painted  with  black  asphaltum  105.5 

Pipe  painted  with  light  drab  lead  paint 108.7 

Glossy  white  paint  95.0 

•"Carpenter's  H.  and  V.  B. 

Note. — These  tests  agree  remarkably  well  with  a  series 
made  by  Prof.  M.  E.  Cooley  of  Michigan  University,  and  also 
with  some  made  by  G.  M.  Brill,  Syracuse,  N.  Y.,  and  reported 
in  Transactions  of  the  American  Society  of  Mechanical  En- 
gineers, Vol.  XVI. 


TABLE   51. 
Factors   of  Evaporation. 


Gage 

.3 

10 

20 

30 

50 

100 

125 

135 

150 

175 

pressure 

Feed 

Factors  of  evaporation 

water 

212 

1.0003 

1.0103 

1.0169 

1.0218 

1.0290 

1.0396 

1.0431 

1.0443 

1.0460 

1.0483 

200 

1.0127 

1.0227 

.0293 

1.0343 

1.0414 

1.0520 

1.0555 

1.0567 

1.0584 

1.0608 

185 

.0282 

1.0882 

.0448 

1.0498 

1.0569 

1.0675 

1.0710 

1.0722 

1.0739 

1.0763 

170 

.0437 

1.0537 

.0603 

1.0653 

1.0724 

1.0830 

1.0865 

1.0877 

1.0894 

1.0917 

155 

.0592 

1.0692 

.0758 

1.0807 

1.0878 

1.0985 

1.1020 

1.1032 

1.1048 

1.1072 

140 

.0715 

1.0846 

.0912 

1.0962 

1.1033 

1.1139 

1.1174 

1.1186 

1.1203 

1.1227 

125 

.0901 

1.1001 

.1067 

1.1116 

1.1187 

1.1293 

1.1328 

1.1341 

1.1357 

1.1381 

110 

.1056 

1.1155 

.1221 

1.1270 

1.1341 

1.1447 

1.1482 

1.1495 

1.1511 

1.1535 

95 

1.1209 

1.1309 

.1375 

1.1424 

1.1495 

1.1602 

1.1637 

1.1649 

1.1665 

1.1689 

80 

1.1363 

1.1463 

.1529 

1.1578 

1.1650 

1.1756 

1.1791 

1.1803 

1.1820 

1.1843 

86 

1.1517 

1.1617 

.1683 

1.1733 

1.1804 

1.1910 

1.1945 

1.1957 

1.1974 

1.1997 

50 

1.1672 

1.1772 

1.1838 

1.1887 

1.1958 

1.2064 

1.2099 

1.2112 

1.2128 

1.2152 

35 

1.1827 

1.1927 

1.1993 

1.2042 

1.2113 

1.2219 

1.2255 

1.2267 

1.2283 

1.2307 

TABLE    52. 

Per  Cent,  of  Total  Heat  of  Steam  Saved  per  Degree  Increase 
of  Feed  Water. 


Initial 


Gage  pressure  in  boiler,  Ibs.  per  sq.  in. 


i/t7iny  . 

of  feed 

0 

20 

40 

60 

80 

100 

120 

140 

160 

180 

32 

.0872 

.0861 

.0855 

.0851 

.0847 

.0844 

.0841 

.0839 

.0837 

.0835 

40 

.0878 

.0867 

.0861 

.0856 

.0853 

.0850 

.0847 

.0845 

.0843 

.0839 

50 

.0886 

.0875 

.0868 

.0864 

.0860 

.0857 

.0854 

.0852 

.0850 

.0846 

60 

.0894 

.0883 

.0876 

.0872 

.0867 

.0864 

.0862 

.0859 

.0856 

.0853 

70 

.0902 

.0890 

.0884 

.0879 

.0875 

.0872 

.0869 

.0867 

.0864 

.0860 

80 

.0910 

.0898 

.0891 

.0887 

.0883 

.0879 

.0877 

.0874  I 

.0872 

.0868 

100 

.0927 

.0915 

.0908 

.0903 

.0899 

.0895' 

.0892 

.0890 

.0887 

.0883 

120 

.0945 

.0932 

.0925 

.0919 

.0915 

.0911 

.0908 

.0906 

.0903 

.0899 

140 

.0963 

.0950 

.0943 

.0937 

.0932 

.0929 

.0925 

.0923 

.0920 

.0916 

160 

.0982 

.0968 

.0961 

.0955 

.0950 

.0946 

.0943 

.0940 

.0937 

.0933 

180 

.1002 

.0988 

.0981 

.0973 

.0969 

.0965 

.0961 

.0958 

.0955 

.0951 

200 

.1022 

.1008 

.0999 

.0993 

.0988 

.0984 

.0980 

.0977 

.0974 

.0969 

220 

.1029 

.1019 

.1013 

.1008 

.1004 

.1000 

.0997 

.0994 

.0989 

240 

.1050 

.1041 

.1034 

.1029 

.1024 

.1020 

.1017 

.1014 

.1009 

Example.— Boiler  pressure  120  Ibs.  gage,  initial  temperature  of  feed 
water  60  deg.,  heated  to  210  deg.  Then  increase  in  temperature  150, 
times  tabular  figure,  .0862,  equals  12.93  per  cent,  saving. 


447 


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TABLE   54. 

Steam   Consumption   of   Various   Types   of   Non-Condensing 
Engines.*      (Approximate). 

Pounds  per  indicated  horse-power  hour. 


Com- 

Com- 

Com- 

Simple 

Simple 

pound 

pound 

pound 

throt- 

auto- 

Simple 

Simple 

four 

four 

four 

Horse- 

tling 

matic 

Corliss 

four 

valve  and 

valve  and 

valve  and 

power 

100  lb,s. 

100  Ibs. 

100  11)S. 

valve 

Corliss 

Corliss 

Corliss 

at 

initial 

initial 

100  Ibs. 

100  Ibs. 

125  Ibs. 

150  Ibs. 

throttle 

initial 

initial 

initial 

initial 

10 

52 

20 

BO 

40.0 

30 

49 

39.0 

40 

48 

38.0 

60 

48 

38.0 

34.5 

35.0 

60 

47 

36.0 

32.5 

33.0 

70 

47 

35.0 

31.5 

32.0 

80 

46 

34.0 

30.5 

31.0 

90 

46 

33.0 

29.5 

30.0 

100 

45 

32.0 

28.5 

29.0 

150 

44 

31.5 

28.0 

28.5 

22.5-23 

21.5-22 

21-21.5 

200 

43 

30.5 

27.0 

27.5 

22-22.5 

21-21.5 

20.5-21 

250 

43 

30.0 

26.5 

27.0 

22-22.5 

21-21.5 

20-20.5 

300 

42 

29.0 

25.5 

26.0 

22-22.5 

20.5-21 

20-20.5 

400 

41 

28.5 

25.0 

25.5 

21.5-22 

20-20.5 

.19.5-20 

500 

41 

28.5 

25.0 

25.5 

20-21.5 

19.5-20 

19-19.5 

The  foregoing  table  was  compiled  principally  from  the  records  of  a 
large  number  of  actual  tests  of  engines  of  various  makes,  under  reason- 
ably favorable  conditions.  It  is  based  upon  the  actual  weight  of  con- 
densed exhaust  steam. 

*  Atlas  Engine  Works  Catalog. 


449 


TABLE   55. 

Speeds,  Capacities  and  Horse-Powers  of  "Green"  Steel  Plate 
Fans  at  Varying  Pressures.* 


11 

Q  fc 

Pressures 

.26  in. 

.87  in.  1.3  in. 

1.7  in. 
loz. 

2.2  in. 

2.6  in.  3.02  in. 

3.46  in. 

4.33  In. 

%  oz. 

%  oz. 

%oz. 

1%OZ 

IV2  oz 

1%OZ. 

2oz. 

2V2  oz. 

CU.  FT. 

2249 

3176 

3891 

4498 

5029 

5513 

5956 

6372 

7135 

30 

R.  P.  M. 

330 

466 

571 

660 

738 

809 

874 

935 

1047 

H.  P. 

.286 

.811 

1.491 

2.298 

3.213 

4.227 

5.311 

6.515 

9.120 

CU.  FT. 

3239 

4581 

5605 

6477 

7242 

7937 

a584 

9173 

10268 

36 

R.  P.  M. 

275 

389 

476 

550 

615 

674 

729 

779 

872 

H.  P. 

.413 

1.170 

2.148 

3.311 

4.625 

6.086 

7.681 

9.375 

13.125 

CU.  FT. 

4398 

6214 

7617 

8815 

9864 

10799 

11679 

12483 

13981 

42 

R.  P.  M. 

235 

332 

407 

471 

527 

577 

624 

667 

747 

H.  P. 

.557 

1.576 

2.898 

5.473 

6.300 

8.287 

10.450 

12.750 

17.825 

CU.  FT. 

5750 

8123 

9937 

11500 

12867 

14123 

15240 

16301 

18282 

48 

R.  P.  M. 

206 

291 

356 

412 

461 

506 

546 

584 

655 

H.  P. 

.733 

2.076 

3.810 

5.880 

8.223 

10.832 

13.636 

16.670 

23.370 

CU.  FT. 

7602 

10758 

13167 

15203 

17030 

18650 

20145 

21558 

24174 

54 

R.  P.  M. 

183 

259 

317 

366 

410 

449 

485 

519 

582 

H.  P. 

.970 

2.750 

5.047 

7.767 

10.880 

14.300 

18.017 

21.992 

30.896 

CU.  FT. 

9715 

13718 

16780 

19429 

21725 

23786 

25728 

27495 

30792 

60 

R.  P.  M. 

165 

233 

285 

330 

369 

404 

437 

467 

523 

H.  P. 

1.241 

3.506 

6.433 

9.932 

13.882 

18.230 

22.996 

28.077 

39.355 

OU.  FT. 

12078 

17071 

20855 

24156 

26975 

29551 

32047 

34221 

38247 

66 

R.  P.  M. 

150 

212 

259 

300 

335 

367 

398 

425 

475 

H.  P. 

1.542 

4.361 

7.996 

12.352 

17.238 

22.666 

28.675 

35.123 

48.895 

CU.  FT. 

15608 

21942 

26918 

31103 

34835 

38115 

41169 

44109 

49312 

72 

R.  P.  M. 

138 

194 

238 

275 

308 

337 

364 

390 

436 

H.  P. 

1.983 

5.601 

10.322 

15.881 

22.252 

29.223 

36.808 

45.043 

62.783 

CU.  FT. 

20192 

28405 

34907 

40383 

45174 

49452 

53387 

57152 

63996 

84 

R.  P.  LI. 

118 

166 

204 

236 

264 

289 

312 

334 

374 

H.  P. 

2.581 

7.262 

13.387 

20.650 

28.875 

37.931 

47.775 

58.450 

81.812 

CU.  FT. 

23008 

32614 

39762 

46016 

51601 

56515 

60983 

65227 

73045 

96 

R.  P.  M. 

103 

146 

178 

206 

231 

253 

273 

292 

327 

H.  P. 

2.941 

8.337 

15.261 

23.531 

32.982 

43.348 

54.511 

66.707 

93.380 

CU.  FT. 

29260 

41027 

50568 

58519 

65198 

71559 

77284 

82690 

92549 

108 

R.  P.  M. 

92 

129 

159 

184 

205 

225 

243 

260 

291 

H.  P. 

3.737 

10.488 

19.397 

30.060 

41.666 

54.871 

69.163 

84.556 

118.291 

OU.  FT. 

36209 

51042 

62384 

71982 

80270 

88550 

95539 

102083 

114298 

120 

R.  P.  M. 

83 

117 

143 

165 

184 

203 

219 

234 

26:> 

H.  P. 

4.628 

13.050 

23.925 

36.807 

51.307 

67.928 

85.495 

104.401 

146.116 

CU.  FT. 

43560 

61565 

75504 

87120 

97575 

106868 

115580 

123711 

138231 

132 

R.  P.  M. 

75 

106 

130 

150 

168 

184 

199 

213 

238 

H.  P. 

5.568 

15.730 

28.957 

44.550 

62.370 

82.096 

103.430 

126.521 

176.715 

CU.  FT. 

52026 

73138 

89726 

103298 

116116 

127426 

137228 

147030 

164372 

144 

R.  P.  M. 

69 

97 

119 

137 

154 

169 

182 

195 

218 

H.  P. 

6.65 

18.700 

34.411 

52.822 

74.221 

97.741 

122.802 

150.371 

210.133 

Manufacturer's  Note.— The  horse-power  required  to  drive  a  fan  will 
vary  according-  to  the  manner  of  application.  The  horse-powers  given 
above  are  25  per  cent,  greater  than  would  be  required  under  ideal  condi- 
tions. 

*  Condensed  from  the  G.  F.  E.  Co.  Catalog. 


450 


TABLE   56. 

Speeds,  Capacities  and  Horse-Powers  of  "A.  B.  C.' 
Plate  Fans  at  Varying  Pressures.* 


Steel 


Fan 

1  Number 

•H 

0 

i| 

of 

Static 

press  . 

w 

1" 

1V2" 

2" 

2W 

3" 

3W 

4" 

.29 
oz. 

.58 
oz. 

.87 
oz. 

1.16 
oz. 

1.44 
oz. 

1.73 
oz. 

2.02 
OZ. 

2.31 
oz. 

O.  F.  M. 

3840 

5425 

6640 

7650 

8595 

9400 

10110 

10810 

50 

30 

R.  P.  M. 

471 

665 

816 

945 

1060 

1150 

1250 

1330 

B.  H.  P. 

.88 

2.48 

4.56 

7.00 

9.81 

12.85 

16.20 

19.75 

0.  F.  M. 

5475 

7740 

9460 

10900 

12250 

13400 

14410 

15420 

60 

36 

R.  P.  M. 

393 

555 

681 

786 

880 

961 

1040 

1110 

B.  H.  P. 

1.25 

3.53 

6.49 

9.94 

14.00 

18.35 

23.10 

28.10 

C.  F.  M. 

7100 

10020 

12280 

14150 

15900 

17400 

18700 

20010 

70 

42 

R.  P.  M. 

336 

475 

583 

675 

755 

825 

890 

9-50 

B.  H.  P. 

1.62 

4.58 

8.35 

12.93 

18.19 

23.80 

29.90 

36.60 

C.  F.  M. 

8640 

12200 

14950 

17200 

19350 

21150 

22800 

24350 

80 

48 

R.  P.  M. 

294 

416 

511 

590 

660 

722 

780 

832 

B.  H.  P. 

1.97 

5.57 

10.20 

15.71 

22.10 

28.90 

36.50 

44.50 

O.  F.  M. 

11000 

15540 

19000 

21900 

24600 

26950 

29000 

31000 

90 

54 

R.  P.  M. 

262 

370 

454 

525 

587 

641 

693 

740 

B.  H.  P. 

2.52 

7.08 

13.00 

20.00 

28.10 

36.85 

46.40 

56.50 

0.  F.  M. 

14050 

19850 

24300 

28000 

31450 

34400 

37000 

39600 

100 

60 

R.  P.M. 

236 

333 

409 

473 

529 

578 

625 

665 

B.  H.  P. 

3.21 

9.05 

•16.65 

25.60 

35.95 

47.10 

59.10 

72.30 

O.  F.  M. 

16600 

23500 

28800 

33100 

37200 

40700 

43800 

46900 

110 

66 

R.  P.M. 

214 

303 

371 

430 

480 

525 

568 

605 

B.  H.  P. 

3.80 

10.75 

19.70 

30.25 

42.50 

55.60 

70.00 

85.60 

C.  F.  M. 

20300 

28700 

35100 

40500 

45500 

49700 

53500 

57300 

120 

72 

R.  P.  M. 

196 

278 

340 

394 

440 

481 

520 

555 

B.  H.  P. 

4.64 

13.10 

24.00 

37.00 

52.00 

68.00 

85.50 

104.50 

O.  F.  M. 

27400 

38700 

47400 

54500 

61300 

67000 

72200 

77250 

140 

84 

R.  P.  M. 

168 

238 

292 

337 

378 

413 

445 

475 

B.  H.  P. 

6.25 

17.75 

32.40 

49.80 

70.00 

91.70 

115.20 

140.9 

C.  F.  M. 

34500 

48900 

59800 

68900 

77300 

84500 

91000 

97500 

160 

96 

R.  P.  M. 

147 

208 

256 

296 

331 

362 

390 

416 

B.  H.  P. 

7.88 

22.30 

41.00 

62.90 

88.40 

115.5 

145.4 

178.0 

O.  F.  M. 

42600 

60300 

73800 

85000 

95500 

104300 

112500 

120000 

180 

108 

R.  P.  M. 

131 

185 

227 

262 

298 

320 

346 

369 

B.  H.  P. 

9.75 

27.55 

50.50 

77.60 

109.0 

143.0 

180.0 

219.0 

C.  F.  M. 

51600 

73000 

89400 

103000 

L15700 

126500 

136100 

145800 

200 

120 

R.  P.  M. 

118 

166 

204 

236 

264 

289 

312 

332 

B.  H.  P. 

11.8 

33.30 

61.20 

93.50 

132.1 

173.0 

217.50 

266.0 

O.  F.  M. 

61400 

86800 

106000 

122200 

137400 

150200 

162000 

173000 

220 

132 

R.  P.  M. 

107 

151 

185 

214 

240 

262 

283 

302 

B.  H.  P. 

14.0 

39.60 

72.50 

111.50 

157.0 

206.0 

259.0 

316.0 

0.  F.  M. 

72000 

101800 

124500 

143500 

161000 

176000 

189500 

203000 

240 

144 

R.  P.  M. 

98 

139 

170 

197 

220 

241 

260 

377 

B.  H.  P. 

16.5 

46.50 

85.00 

131.00 

184.0 

241.0 

303.0 

370.5 

Manufacturer's  Note.— Any  of  the  above  fans,  when  running  at  the 
speed  and  pressure  indicated,  will  deliver  the  volume  of  air  and  require 
no  more  power  than  given  in  the  table. 

Allowances  must  be  made  for  the  inefficiency  of  the  motive  power 
and  for  transmission  losses  between  motive  power  and  the  fan. 

*  Condensed  from  the  A,  B.  C.  Co.  Catalog. 


451 


TABLE   57. 

Speeds,    Capacities    and    Horse-Powers    of   "Sirocco"   Fans    at 
Varying  Pressures.* 


I 

II 

0 

s1® 

11 

Pressures 

in. 

1 
in. 

in* 

in2 

2 
in. 

in. 

3 
in. 

3% 
in. 

4 

in. 

.43 
oz. 

.58 
oz. 

.72 
oz. 

.87 
oz. 

1.16 
oz. 

1.44 
oz. 

1.73 
oz. 

2.02 
oz. 

2.31 
oz. 

C.  F.  M. 

4260 

4920 

5500 

6020 

6945 

7770 

8520 

9200 

9840 

4 

24 

R.  P.  M. 

391 

453 

505 

554 

640 

714 

783 

846 

905 

B.  H.  P. 

.879 

1.348 

1.89 

2.475 

3.8 

5.32 

7.00 

8.825 

10.77 

C.  F.  M. 

6650 

7690 

8600 

9416 

10870 

12150 

13320 

14380 

15380 

5 

30 

R.  P.  M. 

313 

362 

403 

443 

512 

571 

625 

676 

724 

B.  H.  P. 

1.37 

2.105 

2.96 

3.868 

5.95 

8.315 

10.94 

13.80 

16.85 

C.  F.  M. 

9580 

11060 

12350 

13540 

15630 

17470 

19150 

20680 

22150 

6 

36 

R.  P.  M. 

260 

302 

336 

369 

427 

477 

523 

565 

604 

B.  H.  P. 

1.975 

3.03 

4.25 

5.563 

8.56 

11.96 

15.72 

19.85 

24.23 

C.  F.  M. 

13050 

15070 

16800 

18425 

21260 

23800 

26100 

28200 

30140 

7 

42 

R.  P.  M. 

223 

259 

288 

316 

366 

408 

447 

483 

517 

B.  H.  P. 

2.69 

4.126 

5.78 

7.565 

11.66 

16.28 

21.43 

27.06 

33 

C.  F.  M. 

17000 

19700 

22600 

24100 

27820 

31100 

34080 

36800 

39370 

8 

48 

R.  P.  M. 

196 

226 

253 

277 

320 

358 

392 

424 

453 

B.  H.  P. 

3.51 

5.39 

7.58 

9.9 

15.22 

21.30 

28.0 

35.3 

43.15 

C.  F.  M. 

21500 

24860 

27800 

30440 

35140 

39300 

43100 

46600 

49800 

9 

54 

R.  P.  M. 

174 

201 

224 

246 

285 

317 

348 

376 

402 

B.  H.  P. 

4.43 

6.81 

9.57 

12.52 

19.23 

26.94 

35.38 

44.70 

54.5 

C.  F.  M. 

26500 

30750 

34300 

37650 

43400 

48570 

53220 

57500 

61500 

10 

60 

R.  P.  M. 

156 

181 

202 

222 

256 

286 

313 

338 

362 

B.  H.  P. 

5.46 

8.42 

11.8 

15.47 

23.77 

33.23 

43.72 

55.2 

67.4 

C.  F.  M. 

32200 

37200 

41500 

45530 

52550 

58830 

64450 

69630 

74400 

11 

66 

R.  P.  M. 

142 

165 

184 

202 

233 

260 

285 

308 

329 

B.  H.  P. 

6.65 

10.18 

14.3 

18.72 

28.77 

40.24 

52.9 

66.85 

81.5 

C.  F.  M. 

38300 

44240 

49400 

54130 

62500 

69900 

76600 

82800 

88500 

12 

72 

R.  P.  M. 

130 

151 

168 

185 

214 

238 

261 

282 

302 

B.  H.  P. 

7.9 

12.11 

17 

22.25 

34.2 

47.85 

63 

79.5 

97 

C.  F.  M. 

45000 

52000 

58100 

63600 

73500 

82100 

90000 

97300 

104000 

13 

78 

R.  P.  M. 

120 

140 

155 

171 

197 

220 

241 

261 

279 

B.  H.  P. 

9.28 

14.22 

20 

26.16 

40.22 

56.2 

74 

93.35 

113.9 

C.  F.  M. 

52100 

60200 

67300 

73700 

85000 

95000 

104200 

112700 

120400 

14 

84 

R.  P.  M. 

112 

130 

144 

158 

183 

204 

224 

242 

259 

B.  H.  P. 

10.75 

16.49 

23.2 

30.3 

46.6 

65 

85.6 

108 

132 

C.  F.  M. 

59900 

69230 

77500 

84700 

97800 

109200 

119800 

129600 

138500 

15 

90 

R.  P.  M. 

10-1 

121 

135 

148 

171 

191 

209 

226 

242 

B.  H.  P. 

12.34 

18.93 

26.6 

34.8 

53.55 

74.9 

98.5 

124.2 

151.7 

C.  F.  M. 

67S50 

78430 

81800 

96140 

114300 

124500 

136000 

147000 

157300 

16 

96 

R.  P.  M. 

98 

114 

126 

139 

160 

178 

196 

211 

226 

B.  H.  P. 

13.98 

21.5 

30.2 

39.6 

63 

85.7 

112 

142 

173 

*  Condensed  from  A.  B.  C.  Co.  Catalog. 


452 


APPENDIX  II. 


References  used  Chiefly  in  Refrigeration 
and  Ice  Production 


TABLE   58. 
Freezing  Mixtures.* 


Names  and  proportions  of  ingredients 
in  parts 

Reduction  of 
temp.  deg.  F. 

Total 
Reduc- 
tion of 
temp, 
deg.  F. 

Prom 

To 

Snow  or  pounded  ice  2;  sodium  chloride  1    _ 

+32 

+32 
+32 

+32 
+32 

+50 
+50 

+50 
+50 
+50 

+50 

+50 
+50 

+50 

—  5 

—12 
—25 
—40 
—  5 
—23 
—27 
—30 
—51 

+  4 
+  4 

+  4 
+  3 
—  3 

—  7 
10 

72 

55 

59 
62 
83 

46 
46 

46 
47 
53 

57 

60 
62 

64 

Snow  5;  sodium  chloride  2;  ammonium  chloride  1 
Snow  12;  sodium  chloride  5;  ammonium  nitrate  5 
Snow  8;  calcium  chloride  5 

Snow  2;  sodium  chloride  1 

Snow  3;  dilute  sulphuric  acid  2 

Snow  3;  hydrochloric  acid  5  

Snow  7;  dilute  nitric  acid  4  

Snow  3*  potassium  4 

Ammonium  chloride  5;  potassium  nitrate  5; 
water  16 

Ammonium  nitrate  1;  water  1 

Ammonium  chloride  5;  potassium  nitrate  5; 
sodium  sulphate  8;  water  16  

Sodium  sulphate  5;  dil.  sulphuric  acid  4  

Sodium  nitrate  3;  dil.  nitric  acid  2 

Amonium  nitrate  1;  sodium  carbonate  1; 
water  1                           _    _     _ 

Sodium  sulphate  6;  ammonium  chloride  4; 
potassium  nitrate  2'  dil    nitric  acid  4 

Sodium  phosphate  9;  dil.  nitric  acid  4  

—12 

—14 

Sodium  sulphate  6;  ammonium  nitrate  5; 
dil.  nitric  acid  4  ._ 

TABLE   59. 
Properties  of  Saturated   Ammonia.* 


Temp, 
deg.  F. 

Pressure 
absolute 
Ibs.  per 
sq.  in. 

Heat  of 
vaporization 

Vol.  of 
vapor 
per  Ib. 
cu.  ft. 

Vol.  Of 
liquid 
per  Ib. 
cu.  ft. 

Wt.  of 
vapor 
Ibs.  per 
cu.  ft. 

—40 

10.69 

579.67 

24.38 

.0234 

.0411 

—35 

12.31 

576.69 

21.21 

.0236 

.0471 

—30 

14.13 

573.69 

18.67 

.0237 

.0535 

—25 

16.17 

570.68 

16.42 

.0238 

.0609 

—20 

18.45 

567.67 

14.48 

.0240 

.0690 

—15 

20.99 

564.64 

12.81 

.0242 

.0775 

—10 

23.77 

561.61 

11.36 

.0243 

.0880 

—  5 

27.57 

558.56 

9.89 

.0244 

.1011 

+  0 

30.37 

555.50 

9.14 

.0246 

.1094 

+  5 

34.17 

552.43 

8.04 

.0247 

.1243 

+10 

38.55 

549.35 

7.20 

.0249 

.1381 

+20 

47.95 

543.15 

5.82 

.0252 

.1721 

+30 

59.41 

536.92 

4.73 

.0254 

.2111 

+40 

73.00 

530.63 

3.88 

.0257 

.2577 

+50 

88.96 

524.30 

3.21 

.02601 

.3115 

+60 

107.60 

517.93 

2.67 

.0265 

.3745 

+70 

129.21 

511.52 

2.24 

.0268 

.4664 

+80 

154.11 

504.66 

1.89 

.0272 

.5291 

+90 

182.80 

498.11 

1.61 

.0274 

.6211 

+100 

215.14 

491.50 

1.36 

.0279 

.7353 

*Tayler.    Pocket  Book  of  Refrigeration. 

tWood— Thermodynamics,  Heat  Motors  and  Refrigerating  Machines. 


454 


TABLE   60. 

Solubility  of  Ammonia  in  Water  at  Different  Temperatures 
and  Pressures.      (Sims).* 

lib.  of  water  (also  unit  volume)  absorbs  the  following 
quantities  of  ammonia. 


Absolute 

32°  P. 

68°  F. 

104°  F. 

212°  F: 

pressure 

in  Ibs 

per 

sq.  in. 

Lbs. 

Vols. 

Lbs. 

Vols. 

Lbs. 

Vols. 

Grms. 

VolS. 

14.67 

0.899 

1180 

0.518 

683 

0.338 

443 

0.074 

97 

15.44 

0.937 

1231 

0.535 

703 

0.349 

458 

0.078 

102 

16.41 

0.980 

1287 

0.556 

730 

0.363 

476 

0.083 

109 

17.37 

1.029 

1351 

0.574 

754 

0.378 

496 

0.088 

115 

18.34 

1.077 

1414 

0.594 

781 

0.391 

513 

0.092 

120 

19.30 

1.126 

1478 

0.613 

805 

0.404 

531 

0.096 

126 

20.27 

1.177 

1546 

0.632 

830 

0.414 

543 

0.101 

132 

21.23 

1.236 

1615 

0.651 

855 

0.425 

558 

0.100 

139 

22.19 

1.283 

1685 

0.669 

878 

0.434 

570 

0.110 

140 

23.16 

1.336 

1754 

0.685 

894 

0.445 

584 

0.115 

151 

24.13 

1.388 

1823 

0.704 

924 

0.454 

596 

0.120 

157 

25.09 

1.442 

1894 

0.722 

948 

0.463 

609 

0.125 

164 

26.06 

1.496 

1965 

0.741 

973 

0.472 

619 

0.130 

170 

27.02 

1.549 

2034 

0.761 

999 

0.479 

629 

0.135 

177 

27.99 

1.603 

2105 

0.780 

1023 

0.486 

638 

28.95 

1.656 

2175 

0.801 

1052 

0.493 

647 

30.88 

1.758 

2309 

0.842 

1106 

0.511 

671 

32.81 

1.861 

2444 

0.881 

1157 

0.530 

696 

34.74 

1.966 

2582 

0.919 

1207 

0.547 

718 

36.67 

2.070 

2718 

0.955 

1254 

0.565 

742 

TABLE   61. 
Strength  of  Ammonia  IJquor.* 


Degrees 
Baume 

Specific 
gravity 

Percent- 
age 

Degrees 
Baume 

Specific 
gravity 

Percent- 
age 

10 

1.0000 

0.0 

20 

0.9333 

17.4 

11 

0.9929 

1.8 

21 

0.9271 

19.4 

12 

0.9859 

3.3 

22 

0.9210 

21.4 

13 

0.9790 

5.0 

23 

0.9150 

23.4 

14 

0.9722 

6.7 

24 

0.9090 

25.3 

15 

0.9655 

8.4 

25 

0.9032 

27.7 

16 

0.9589 

10.0 

26  (a) 

0.8974 

30.1 

17 

0.9523 

11.9 

27 

0.8917 

32.5 

18 

0.9459 

13.7 

28 

0.8860 

35.2 

19 

0.9396 

15.5 

29 

0.8805 

Note. — Sp.  gr.  of  pure  anhydrous  ammonia  =  .623. 
(a)  Known  to  the  trade  as  "29%  per  cent." 
*Tayler.     Pocket-Book  of  Refrigeration. 


455 


TABLE   62. 
Properties    of    Saturated   Sulphur   Dioxide. 


(L,edoux).* 


Absolute 

Temp,  of 
ebullition 

pressure 
Ibs.  per. 

Total  heat 
from 

Latent  heat 
of  vapor- 

Heat of 
liquid 

Density  of 
vapor 

deg.  F. 

sq.  in. 

32  deg.  F. 

ization 

from 

wt.  per 

P4-  144 

32  deg.  F. 

cu.  ft. 

—22 

5.56 

157.43 

176.99 

—19.56 

.076 

—13 

7.23 

158.64 

174.95 

—16.30 

.097 

—  4 

9.27 

159.84 

172.89 

—13.05 

.123 

5 

11.76 

161.03 

170.82 

—  9.79 

.153 

14 

14.74 

162.20 

168.73 

—  6.53 

.190 

23 

18.31 

163.36 

166.63 

—  3.27 

.232 

32 

22.53 

164.51 

164.51 

0.00 

.282 

41 

27.48 

185.65 

162.38 

1     3.27 

.340 

50 

33.25 

166.78 

160.23 

6.55 

.407 

59 

39.93 

167.90 

158.07 

9.83 

.483 

68 

47.61 

168.99 

155.8!) 

13.11 

.570 

77 

56.39 

170.09 

153.70 

16.39 

.089 

86 

66.36 

171.17 

151.49 

19.69 

.780 

95 

77.64 

172.24 

149.26 

22.98 

.906 

104 

90.31 

173.30 

147.02 

26.28 

1.046 

TABLE   63. 
Properties  of  Saturated  Carbon  Dioxide.t 


Absolute 

Temp,  of 

pressure 

Total  heat 

Latent  heat 

Heat  of 

Density  of 

ebullition 

in  Ibs. 

from 

of  vapor- 

liquid 

vapor  or 

deg.  F. 

per 
sq.  in. 

32  deg.  F. 

ization 

from 
32  deg.  F. 

wt.  per 
cu.  ft. 

22 

210 

98.35 

136.15 

—37.80 

2.321 

—13 

249 

99.14 

131.65 

—32.51 

2.759 

—  4 

292 

99.88 

126.79 

—26.91 

3.265 

5 

342 

100.58 

121.50 

—20.92 

3.853 

14 

396 

101.21 

115.70 

—14.49 

4.535 

23 

457 

101.81 

109.37 

1    —  7.56 

5.331 

32 

525 

102.35 

102.35 

0.00 

6.265 

41 

599 

102.84 

94.52 

8.32 

7.374 

50 

680 

103.24 

85.64 

17.60 

8.708 

59 

768 

103.59 

75.37 

28.22 

10.356 

68 

864 

103.84 

62.98 

40.86 

12.480 

77 

968 

103.95 

46.89 

57.06 

15.475 

86 

1080 

103.72 

19.28 

84.44 

21.519 

*Kents'  M.  E.  Pocket-Book. 
tl.  C.  S.  Pamphlet  1238,B. 


456 


TABLE    64. 

Pressures  and   Boiling:    Points   of   Liquids   Available   for   Use 
in  Refrigerating;  Machines.4 


Tempera- 
ture of 
ebullition 

Pressure  of  vapor 
Pounds  per  square  inch  absolute 

deg.  F. 

Sulphur 

Ammonia 

Carbon 

Pictet 

dioxide 

dioxide 

fluid 

—  10 

10.22 

—31 

13.23 

.22 

5.56 

16.95 

—13 

7.23 

21.51 

251.6 

—  4 

9.27 

27.04 

292.9 

13.5 

5 

11.76 

33.67 

340.1 

16.2 

14       • 

14.75 

41.58 

393.4 

19.3 

23 

18.31 

50.91 

453.4 

22.9 

32 

22.53 

61.85 

520.4 

26.9 

41 

27.48 

74.55 

594.8 

31.2 

50 

33.26 

89.21 

676.9 

36.2 

59 

39.93 

105.99 

766.9 

41.7 

68 

47.62 

125.08 

864.9 

48.1 

77 

56.39 

146.64 

971.1 

55.6 

86 

66.37 

170.83 

1085.6 

64.1 

95 

77.64 

197.83 

1207.9 

73.2 

104 

90.32 

227.76 

1338.2 

82.9 

TABLE   65. 
Table  of  Calcium  Brine  Solution.t 


Deg. 

Per  cent. 

Baume 

calcium 

Lbs.  per 

Specific 

Specific 

Freezing 

Amm. 

60  deg. 

by 

cu.  ft. 

gravity 

heat 

point 

gage 

F. 

weight 

solution 

deg.  F. 

pressure 

0 

0.000 

0.0 

1.000 

1.000 

32.00 

47.31 

2 

1.886 

2.5 

1.014 

OftQ 

30.33 

45.14 

4 

3.772 

5.0 

1.028 

!972 

28.58 

43.00 

6 

5.658 

7.5 

1.043 

.955 

27.05 

41.17 

8 

7.544 

10.0 

1.058 

.936 

25.52 

39.35 

10 

9.430 

12.5 

1.074 

.911 

22.80 

36.30 

12 

11.316 

15.0 

1.090 

.890 

19.70 

32.93 

14 

13.202 

17.5 

1.107 

.878 

16.61 

29.63 

16 

15.088 

20.0 

.124 

.866 

13.67 

27.04 

18 

16.974 

22.5 

.142 

.854 

10.00 

23.85 

20 

18.860 

25.0 

.160 

.844 

4.60 

19.43 

22 

20.746 

27.5 

.179 

.834 

—  1.40 

14.70 

24 

22.632 

30.0 

.198 

.817 

—  8.60 

9.96 

26 

24.518 

32.5 

.218 

.799 

—17.10 

5.22 

28 

26.404 

35.0 

.239 

'      .778 

—27.00 

.65 

30 

28.290 

37.5 

.261 

.757 

—39.20 

8.  5"  vac. 

32 

30.176 

40.0 

1.283 

—54.40 

15"     vac. 

34 

32.062 

42.5 

1.306 

—39.20 

4"     vac. 

*  Kent's  M.  E.  Pocket-Book. 

t  Am.  Sch.  of  Cor.  Dickerman-Boyer. 


457 


TABLE   66. 
Table  of  Salt  Brine  Solution.4 

(Sodium   chloride). 


Degrees 
Salom- 
eter  at 
60  deg.  F. 

Percent, 
by  wt. 
of  salt 

Pounds 
of  salt 
per  cu.  ft. 

Specific 
gravity 

Specific 
heat 

Freezing 
point 
deg.  F. 

Amm. 
gage 
pressure 

0 

0.00 

0.000 

1.0000 

1.000 

32.0 

47.32 

5 

1.25 

0.785 

.0090 

.990 

30.3 

45.10 

10 

2.50 

1.586 

.0181 

.980 

28.6 

43.03 

15 

3.75 

2.401 

.0271 

.970 

26.9 

41.00 

20 

5.00 

3.239 

.0362 

.960 

25.2 

38.96 

25 

6.25 

4.099 

.0455 

.943 

23.6 

37.19 

30 

7.50 

4.967 

.0547 

.926 

22.0 

35.44 

35 

8.75 

5.834 

.0640 

.909 

20.4 

33.69 

40 

10.00 

6.709 

.0733 

.892 

18.7 

31.93 

45 

11.25 

7.622 

.0828 

.883 

17.1 

30.33 

50 

12.50 

8.542 

.0923 

.874 

15.5 

28.73 

55 

13.75 

9.462 

.1018 

.864 

13.9 

27.24 

60 

15.00 

10.389 

.1114 

.855 

12.2 

25.76 

65 

16.25 

11.384 

.1213 

.848 

10.7 

24.46 

70 

17.50 

12.387 

.1312 

.842 

9.2 

23.16 

75 

18.75 

13.396 

.1411 

.835 

7.7 

21.82 

80 

20.00 

14.421 

1.1511 

.829 

6.1 

20.43 

85 

21.25 

15.461 

1.1614 

.818 

4.6 

19.16 

90 

22.50 

16.508 

1.1717 

.806 

3.1 

18.20 

95 

23.75 

17.555 

1.1820 

'  .7!>r> 

1.6 

16.88 

100 

25.00 

18.610 

1.1923 

.783 

0.0 

15.67 

TABLE   67. 
Horse-Power  Required  to  Produce  One  Ton  of  Refrigeration.! 

Condenser  pressure  and  temperature. 


P 

103 

115 

127 

139 

153 

168 

184 

200 

218 

s  p 

T 

65 

70 

75 

80 

85 

90 

95 

100 

105 

73  4 

—20° 

1.0584 

1.1304 

1.2051 

1.2832 

1.3611 

1.4427 

1.5251 

1.6090 

1.6910 

§  6 

—15 

.9972 

1.0694 

1.1450 

1.2221 

1.3001 

1.4101 

1.4609 

1.5458 

1.6300 

•  9 

—10 

.9026 

.9777 

1.0453 

1.1183 

1.1926 

1.2602 

1.3471 

1.4352 

1.5093 

w  13 

—  5 

.8184 

.8833 

.9537 

1.0230 

1.0935 

1.1679 

1.2437 

1.3209 

1.3961 

£  16 

0 

.7352 

.8008 

.8648 

.9328 

1.0019 

1.0718 

1.1467 

1.2194 

1.2547 

?  20 

5 

.6665 

.7312 

.7946 

.8593 

.9278 

.9978 

1.0656 

1.1381 

1.2121 

5  24 

10 

.5915 

.6629 

.7257 

.7894 

.8545 

.9205 

.9911 

1.0595 

1.1294 

«  28 

15 

.5410 

.5998 

.6641 

.7276 

.7924 

.8553 

.9224 

.9943 

1.0603 

|33 

20 

.4745 

.5340 

.5923 

.6716 

.7148 

.7796 

.8420 

.9031 

.9736 

25 

.4103 

.4659 

.5227 

.5804 

.5992 

.7022 

.7667 

.8289 

.8922 

•a  45 

30 

.3509 

.4056 

.4612 

.5178 

.5755 

.6353 

.6944 

.7590 

.8172 

(3  51 

35 

.3005 

.3546 

.4101 

.4666 

.5214 

.5804 

.6398 

.7009 

.7629 

Note.— The  above  figures  are  purely  theoretical. 
50  per  cent,  must  be  added. 

*Am.  Sen.  of  Cor.  Dickerman-Boyer. 
t  De  La  Vergne  Catalog. 

458 


In  practice  about 


TABLE   68. 

Cubic  Feet  of  Ammonia  Gas  per  Minute  to  Produce  One  Ton 
of  Refrigeration  per  Day.* 

Condenser  pressure  and  temperature. 


TJ 

5 

Press. 

103 

115 

127   |    139 

153 

168 

185 

200 

218 

Press. 

Temp. 

65° 

70° 

75°    |    80° 

85° 

90° 

95° 

100° 

105° 

8 

4 

—20° 

5.84 

5.90 

5.96 

6.03 

6.06 

6.16 

6.23 

6.30 

6.43 

§  £ 

6 

—15° 

5.35 

5.40 

5.46 

5.52 

5.58 

5.64 

5.70 

5.77 

5.83 

g  D 

9 

—10° 

4.66 

4.73 

4.76 

4.81 

4.86 

4.91 

4.97 

5.05 

5.08 

p,«3 

13 

—  5° 

4.09 

4.12 

4.17 

4.21 

4.25 

4.30 

4.35 

4.40 

4.44 

.    « 

16 

0° 

3.59 

3.63 

3.66 

3.70 

3.74 

3.78 

3.83 

3.87 

3.91 

0& 

20 

5° 

3.20 

3.24 

3.27 

3.30 

3.34 

3.38 

3.41 

3.45 

3.49 

11 

24 

10° 

2.87 

2.90 

2.93 

2.96 

2.99 

3.02 

3.06 

3.09 

3.12 

o 

28 

15° 

2.59 

2.61 

2.65 

2.68 

2.71 

2.73 

2.76 

2.80 

2.82 

bo 

33 

20° 

2.31 

2.34 

2.36 

2.38 

2.41 

2.44 

2.46 

2.49 

2.51 

S 

39 

25° 

2.06 

2.08 

2.10 

2.12 

2.15 

2.17 

2.20 

2.22 

2.24 

t§ 

45 

30° 

1.85 

1.87 

1.89 

1.91 

1.93 

1.95 

1.97 

2.00 

2.01 

51 

35° 

1.70 

1.72 

1.74 

1.76 

1.77 

1.79 

1.81 

1.83 

1.85 

TABLE   69. 
Table  of  Refrigerating  Capacities.! 


Size  of  building 


Number  of  cu.  ft.  per  ton  of  refrigera- 
tion at  temperatures  given 


Dimen- 

Con- 

Sur- 
face 

Ratio 
cu.ft. 

Temperatures 

sions  of 

tents 

in  sq. 

to  sq. 

building 

cu.  ft. 

ft. 

ft. 

0° 

8° 

16° 

24° 

32° 

40° 

48° 

5x4x5 

100 

130 

1.3 

900 

1100 

1300 

1500 

1700 

1900 

2100 

8x10x10 

800 

520 

.65 

1800 

2200 

2600 

3000 

3400 

3800 

4200 

25x40x10 

10000 

3300 

.33 

3600 

4400 

5200 

6000 

6700 

7600 

8400 

20x50x20 

20000 

4800 

.24 

4860 

5940 

7020 

8100 

9180 

10260 

11340 

40x50x20 

40000 

7600 

.19 

6300 

7700 

9100 

10500 

11900 

13300 

14700 

60x50x20 

60000 

10400 

.17 

6840 

8360 

9880 

11400 

12920 

14440 

15960 

80x50x20 

80000 

13200 

.165 

7200 

8800 

10700 

12000 

13600 

15200 

16800 

100x50x20 

100000 

16000 

.16 

7200 

8800 

10400 

12000 

13600 

15200 

16800 

100x100x20 

200000 

28000 

.14 

8100 

9900 

11700 

13000 

15300 

17100 

18900 

100x100x40 

400000 

36000 

.09 

13050 

15950 

18850 

21750 

24650 

27550 

30450 

100x100x60 

600000 

44000 

.073 

16200 

19800 

23400 

27000 

30600 

34200 

37800 

100x100x80 

800000 

52000 

.065 

18000 

22000 

26000 

30000 

34000 

38000 

42000 

100x100x100 

1000000 

60000 

.06 

19350 

23650 

27950 

32250 

36550 

40850 

45150 

*  Featherstone  Foundry  and  Machine  Co.  Catalog. 
tTayler.    P.  B.  of  B. 


459 


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rH      e<i      e^      co      co      •>»      -^ 

g 

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to 

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co       0       00       Oi       (M       CO       <M 

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s 

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460 


TABLE   71. 

Temperatures  to  Which  Ammonia  Gas  Is  Raised  by 
Compression.* 


Tempera- 

Absolute 

Absolute  suction  pressure 

ture  of 
suction 

3onQGiising' 
pressure 

20 

25 

30 

35 

40 

45 

0  deg.  F. 

90 

199 

165 

138 

116 

98 

83 

110 

232 

196 

166 

145 

126 

109 

130 

261 

222 

193 

169 

150 

132 

150 

285 

246 

216 

191 

171 

153 

160 

296 

257 

226 

202 

181 

163 

5  deg.  F. 

90 

266 

172 

145 

123 

104 

89 

110 

239 

203 

174 

151 

132 

115 

130 

268 

230 

200 

176 

156 

139 

150 

203 

254 

223 

198 

178 

160 

160 

305 

265 

234 

209 

188 

170 

10  deg.  F. 

.  90 

213 

178 

151 

129 

110 

96 

110 

247 

210 

181 

158 

139 

122 

130 

275' 

237 

207 

183 

163 

145 

150 

301 

262 

231 

205 

185 

167 

160 

313 

273 

241 

216 

195 

176 

15  deg.  F. 

90 

221 

185 

158 

135 

117 

101 

110 

254 

217 

188 

164 

145 

128 

130 

283 

245 

214 

191 

170 

152 

150 

309 

269 

238 

213 

192 

173 

160 

321 

281 

249 

223 

202 

^183 

20  deg.  F. 

90 

228 

192 

164 

141 

123 

106 

110 

262 

224 

195 

171 

150 

134 

130 

291 

252 

222 

197 

176 

158 

150 

317 

277 

245 

220 

198 

180 

160 

329 

288 

256 

230 

209 

190 

25  deg.  F. 

90 

235 

199 

171 

148 

129 

111 

110 

269 

230 

200 

178 

155 

140 

130 

299 

259 

229 

204 

183 

165 

150 

325 

284 

253 

227 

205 

187 

160 

338 

298 

264 

237 

216 

197 

30  deg.  F. 

90 

242 

206 

177 

154 

134 

118 

110 

277 

239 

208 

184 

164 

147 

130 

307 

267 

236 

211 

190 

171 

150 

334 

292 

260 

234 

212 

193 

160 

346 

304 

271 

245 

223 

203 

35  deg.  F. 

90 

249 

213 

182 

160 

141 

124 

no 

286 

246 

215 

191 

170 

153 

130 

315 

274 

243 

217 

196 

178 

150 

341 

300 

268 

241 

219 

200 

160 

354 

312 

279 

252 

230 

210 

*Tayler.    P.  B.  oi  R. 


461 


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CO 

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so 
1 

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1 

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§ 

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CO 

.        CO 
CO 

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in 
$ 

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CO 

CJ 

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8 

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g 

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S3 

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in 

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CM 

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m 

rH 

o 

3 

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o 

CM 

oo 

0 

in 

rH 

d 

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rH 

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5 

CO 

in 

si 

a 

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00 

co" 

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CO 
CO 

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01 

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in 

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5 

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o 

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0 

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0 

rH 

rH 

rees  Baume 

PH 

6 

?n 
in 

& 

r-f 

3 

7 

h& 

s| 

«H        II 

a  ? 

6       g 

fis      II 

ix.  Saccharimetric. 
cent,  sugar) 

.     11 

^iquids  heavier  than 
water 
145 
sp.  gr.  = 
145  —  B° 

1  0  « 

S  |        1| 

2         be 

D"              ft 

3       * 

ft 

.S 

cSS 

^o 
S  * 

1 

•s 

111 

££      <* 

Wa 

0      ^ 

coo 
J3  ^^ 

1 

^ 

EH 

Is  » 

"3 

1 

r 

0}          03 
OQ 

§ 

Otf  009) 
•ossy  'ta« 

•o  oS-gi 
qo  -s  -a 

1 

0 

bo 

0 

0 

S 

CS 

O 

^;IAB 

462 


TABLE   73. 
Time  Required  to  Freeze  Ice  in  Cells  or  Cans,  (a)    (Sieberi).* 


Temp, 
deg.  F. 

Thickness  in  inches 

1 

2 

3 

4 

5 

6 

11.5 
12.6 
14.0 
15.8 
18.0 
21.0 
25.2 
31.5 

7 

8 

9 

10 

11 

12 

45.8 
50.4 
56.0 
63.0 
72.0 
84.0 
100.0 
126.0 

10 
12 
14 
16 
18 
20 
22 
24 

0.32 
0.35 
0.39 
0.44 
0.50 
0.53 
0.70 
0.88 

1.28 
1.40 
1.56 
1.75 
2.00 
2.32 
2.80 
3.50 

2.86 
3.15 
3.50 
3.94 
4.50 
5.25 
6.30 
7.86 

5.10 
5.60 
6.22 

7.00 
8.00 
9.30 
11.20 
14.00 

8.00 
8.75 
9.70 
11.00 
12.50 
14.60 
17.50 
21.00 

15.6 
17.3 
19.0 
21.5 
24.5 
28.5 
34.3 
42.8 

20.4 
22.4 
25.0 
28.0 
32.0 
37.3 
44.8 
56.0 

25.8 
28.4 
31.5 
35.5 
40.5 
47.2 
56.7 
71.0 

31.8 
35.0 
39.0 
43.7 
50.0 
58.3 
70.0 
87.5 

38.5 
42.3 
47.0 
53.0 
60.5 
70.5 
84.7 
106.0 

(a)  Time  required  from  one  wall,  for  plate  ice,  two  times  the  above  values. 

TABLE   74. 
Standard  Sizes  of  Ice  Cans.t 


Size  of 
cake,  in 
pounds 

Size  of 
top, 
inches 

Size  of 
bottom, 
inches 

Inside 
depth, 
inches 

Outside 
depth, 
inches 

Size  of 
band, 
inches 

50 

100 
200 
300 

400 

8x8 
8x16 

liy2x22i/2 

ny2x22y2 

Il%x22y2 

7%x7y2 
7^x151,4 

ioy2x2iy2 
ioy2x2iy2 

10^x21% 

31 

31 
31 
44 
57 

32 
32 
32 
45 

58 

%xiy2 
y4xiy2 
14x2 

%x2 
^4x2 

TABLE   75. 
Cold  Storage  Temperatures  for  Various  Articles.* 


Article 

Temp, 
deg. 
F. 

Article 

Temp, 
deg. 
F. 

Article 

Temp. 

dlg- 

Apples 

32-36 

Fruits 

26-55 

45-50 

Asparagus   _    _ 

34 

Fruits  (dried) 

35-40 

Oysters 

33-35 

Bananas     _  

40-45 

Fruits  (canned) 

35 

Oysters  (in 

Beans  (dried)  __ 
Berries  (fresh) 

32-40 
36-40 

Furs  (un- 
dressed) 

35 

tubs)    
Oysters  (in 

25 

Buclrwheat 

Furs  (dressed)  _ 

25-32 

shells) 

33 

flour 

40 

Game  (frozen) 

25-^8 

45-55 

Butter 

32  38 

Game  (to 

Pears 

34  36 

Cabbage  

34 

freeze) 

15-28 

Peas  (dried) 

40 

Cantaloupes  

40 

Grapes  

36-38 

Pork 

34 

Celery 

32-34 

Hams 

30-35 

Potatoes 

36-40 

Cheese  

32-33 

Hops 

33-40 

Poultry 

Chocolate    __. 

40 

Honey     

45 

(frozen) 

28-30 

Cider  __      

30-40 

Lard 

34-45 

Poultry  (to 

Claret    

45-50 

Lemons 

36-40 

freeze) 

18-22 

Corn    (dried)    _. 
Cranberries  

35 

34-36 

Meat  (canned).- 
Meat  (fresh) 

35 
34 

Sugar,  etc.  

40-45 
35 

Cream 

35 

Meat  (frozen) 

25-28 

35 

Cucumbers 

39 

Milk  

32 

Tomatoes 

36 

Dates    

55 

Nuts 

35 

Vegetables 

34  40 

Eggs 

33-35 

Oat  meal 

40 

34 

Figs 

55 

Oil 

35 

Wheat  flour 

40 

Fish  (fresh)  ___ 

25-30 

Oleomargarine 

35 

Wines 

40-45 

Fish  (dried)  ___ 

35 

Onions  

34-40 

Woollens,   etc... 

25-32 

*Tayler.    P.  B.  of  R. 

t  As  adopted  by  the  Ice  Machine  Builders'  Association  of  the  U.  S. 
463 


APPENDIX  III. 


Tests  of  House  Heating*  Boilers. 

The  following-  extract  from  a  series  of  tests  on  a  Num- 
ber S-48-7  Ideal  Sectional  Boiler  from  the  reports  of  the 
American  Radiator  Company's  Institute  of  Thermal  Re- 
search, Buffalo,  New  York,  will  be  of  interest. 

Size  of  Grate 48x64^  in.      .Grate  area 21.6sq.  ft. 

Heating  surface— total 300. Osq.  ft. 

Hard      Hard      Hard 

0— .Fuel  used  in  tests  Coal       Coal       Coal 

1— No.  of  boiler S-48-7     S-48-7     S-48-7 

2— Duration  of  test  hours  8:00         7:00         8:00 

4— Fuel  burned  during  test,  Ibs 1360.00    1344.00    1434.00 

5— Fuel  per  hour,  Ibs.   170.00      192.00      178.20 

6— Fuel  per  sq.  ft.  grate  per  hour,  Ibs 7.90         8.95         8.35 

7— Stack  temperature,  degrees  Fahrenheit 750.00     725.00     600.00 

8— Evaporation  per  sq.  ft.  of  heating  surface 

per  hour,  Ibs.   4.97         5.60         5.24 

9 — Evaporative  power  available — Ibs.  of  water 

per  Ib.  of  coal  8.80         8.75         8.77 

10— Boiler-power  (evaporation  per  hour)— Ibs. 

(item  5  x  item  9)  1496.00    1680.00    1562.00 

11— Capacity— sq.  ft.  (item  10  4-  0.22) 6800.00    7640.00    7100.00 

12— Capacity— sq.  ft.  (item  10  4-  0.25) 5980.00    6720.00    6250.00 

Catalog  rating 1 5700  sq.  ft. 

The  accompanying  figure  shows  the  combustion  chart 
as  developed  for  this  same  boiler.  The  tests  were  run  to 
find  the  evaporative  power  and  ca- 
ixidti/  with  varying  amounts  of 
coal  burned  per  hour.  Coal  was 
fired  at  regular  intervals  and  the 
steam  pressure  was  maintained  at 
two  pounds  gage  on  the  radiation. 
Line  11  gives  the  capacity  in 
square  feet  of  radiation  including 
mains  and  risers,  at  the  rate  of 
.22  pound  of  steam  per  square 
foot  per  hour.  Line  12  gives  the 
capacity  at  .25  pound  of  steam  per 
square  foot  per  hour.  In  average 
service  about  one-third  of  therse 

quantities  of  coal  would  be  burned.  The  catalog-  rating  is 
based  upon  burning  167.5  pounds  of  coal  per  hour  and  an 
evaporation  of  8.5  pounds  of  water  per  pound  of  coal  (rates 
of  combustion  and  evaporation  that  seem  justifiable).  As 
will  be  seen  from  lines  5  and  9  the  actual  amount  of  coal 

465 


burned  and  the  actual  evaporation  in  each  test  exceed  this 
figure.  Multiplying  167.5  by  the  assumed  evaporative  rate 
of  8.5  and  dividing  by  .25  =  5700  square  feet.  Comparing 
with  column  2,  line  5  times  line  9  divided  by  .25  gives  6720 
square  feet,  which  is  above  the  catalog  rating.  Test  number 
two  compared  with  test  number  one  shows  that  by  increas- 
ing the  amount  of  coal  from  170  pounds  to  192  pounds  per 
hour  increases  the  boiler  capacity  740  square  feet. 


Data  Required  for  Estimating  Plain  Hot  Water  or 
Steam  Plants. 


Name 
of 
room 

1  Location  ex- 
posed or  not 

Sizeoi 
room 

Cubic  contents 

03 

£ 

"So 

? 

<}H 

cr 
cc 

a 

OS 

£ 
cr 

OQ 

Radiators 
Steam  or  water 

Remarks: 
Cold  floor, 
ceiling,  etc. 

be 

I 

1 

•a 

X 

I 

-u 

•»§ 

ii 

5l 

T2 

a 

i—  i 

Number 

| 

£ 

£Z 

B 

Date 192— 

Owner  of  building- Address 

Architect  Address 

Kind  of  building Location 

Nearest  freight  station 

Temperature  in  living  rooms. Kind  of  fuel  used- 
Height  of  cellar Size  of  smoke  flue. 

Items  to  Estimate  on. 

Boiler  and  foundation 

Smoke  pipe  and  damper 

Thermometers  and  pressure  and  safety  gages 

Draft  regulation 

Firing  tools ,_ 

Filling  and  blow-off  connection 

Pipe  and  fittings 


.in. 


Sq.  ft.  of  radiation 

Cut-off  valves  and  radiator  valves 

Air  valves  

Radiator  wall  shields _ _. 

Temperature  control   _ _ 

Humidifying  apparatus  

Floor  and  ceiling  plates 

Hangers  

Expansion  tank 

Cold  air  ducts,  stack  boxes  and  registers- 
Pipe  covering 

Bronzing   

Labor  of  installation 

Freight  and  cartage 

Per  cent,  of  profit _. 

Total  bid 

Submitted  by  .. 


467 


SKETCHES    SHOWING   VACUUM    SERVICE    DETAILS.* 


ELEVATION-END  OUTLETS. 

A  B 

Method   of  installing-  return   connections   from   overhead 
manifold  coils,  using-  drop  legs,  traps  and  dirt  strainers. 
A  for  6  coils  or  less,  B  for  more  than  6  coils. 


TO  HEATIN6  5UPPLV  MAIN 


C.  Method  of  installing  drip  connections  from  horizontal 
oil  separator  through  grease  and  oil  trap  to  drain. 

I).  Method  of  dripping  steam  supply  main  through  drip 
trap  into  vacuum  return,  using  vertical  loop  as  cooling  sur- 
face and  dirt  pocket. 


'Warren  Webster  Co. 


468 


CONNfCT  TO  LOW  PPE55UPE  HEATING  MAIN  NOT  LC55 
fHAh  IS'OIJTANT  FROM  PBDSUgC  gEGULATINlj  VALVE     I 


NOTE  .purAMtf  ncngcji  PUW  Hpu.r  ANO^UCTION  vAivc3 

Of  MlCt?  fEEO  PUMP  TO  K|<OT  LtM  THAN  J-Q' 

E  F 

E.  Method  of  draining-  down  feed  supply  risers  through 
wet  return  into  a  feed  water  heater. 

F.  Method  of  making  connections  to  gages. 


G.     Method  of  installing  a  suction  strainer  where  return 
main   rises   to  vacuum   pump,   using   fittings   for  lift   pocket. 

H.     Method  of  draining  a  hot  water  generator  through  a 
gate  valve,  dirt  strainer  and  heavy  duty  trap. 


469 


I.  Method  of  installing-  connections  where  dry  return 
rises  and  drips  into  wet  returns. 

J.  Detail  showing  return  connection  from  radiators  on 
brackets  to  wet  return  near  floor  with  air  line  connections 
through  air  line  trap  into  dry  return  near  ceiling. 


K  L 

K.     Method  of  installing  drip  connection  at  end  of  sup- 
ply main,  or  end  of  a  long  supply  main  branch. 

Li.     Arrangement  of  return  for  modulation  system  where 
steam  is  taken  from  outside  source. 


470 


INDEX 


Absolute  pressure  15 

temperature  14 
Absorption  system  of  refrig.  364 

absorbers  370 

compared  with  compression  sys.  372 

coolers  for  371 

condensers  for  369 

elevation  of  366 

exchang-ers  for  371 

pumps  for  371 

Accelerated  systems,  hot  water  187 
Adaptation  of  district  steam  to  pri- 
vate plants  338 
Air,  amount  to  burn  fuels  26 

circulation,  furnace  system  78,  112 

composition  35 

duct,  fresh  83 

effect  upon  persons  44 

exhausted,  from  nozzle,  actual  254 

exhausted  per  hour,  plenum  sys.  235 

hot,  radiator)  systems  115 

h.  p.  in  moving'  253,  257 

humidity  of  46 

leakage,  heat  loss  by  67 

moisture  required  by  51 

needed,  plenum  system  235 

purification  43 

required  as  heat  carrier  78 

required  per  person  40,  42 

temperature  at  register  85 

valves  161 

velocities,  measurement  of  54,  249 

velocities  of,  in  convection  52 

velocities,  plenum  system  249,  237 

washing  and  humidifying  46,  95,  230 
Ammonia,  for  one-ton  refrig.  459 

solubility  in  water  455 

strength  of  liquor  455 
Anchors,  types  of  288 
Anemometer  54 
Appendix  I,  tables  1  to  57 

for  heating  and  ventilation  399 
Appendix  II,  tables  58  to  75 

for  refrigeration  453 
Appendix  III,  Boiler  tests,  data  for 
estimating   heating   plants,    vac- 
uum piping  details  464 
Application  of  heat  to  solids  and 
liquids  20 

of  heat  to  gases  24 
Area  of  chimney,  determination  of  57 

of  ducts,  furnace  system  82 

of  ducts,  indirect  system  171,  173 

of  ducts,  plenum  system  237 

of  furnace  and  boiler  grates  84,  148, 
166 


Aspirating  coils  176 
Atmospheric  and  vapor  systems  130 
Automatic  vacuum  sys.  203 
valves  209 

Bishop  and  Babcock  sys.  203 
Blast  coils,  see  Coils. 
Blowers,  see  Fans. 
Boiler,  feeding  193,  317 

efficiencies  31 

feed  pumps  317 

fittings  149 

types  144,  319 
Boilers,  h.  w.  and  st.  144,  319 

capacity  and  number  of  323 

care  and  use  of  199 

radiation  supplied  by  166,  320 

rating  of  166,  320 

tests  of  465 
Boiling  point  of  water  21,  412,  415 

of  liquids  457 
Boyle's  law  25 

Brine  cooling  system,  cap.  of  385 
British  thermal  unit  11,  16 
Broomell  sys.  133 
Bruckner  system  138 
B.  t.  u.  defined  10 

equivalents  11 

lost  from  buildings  73 
Build,  materials,  conductivities  of  63 

Calcium  brine  solution  457 
Calorie,  defined  10 

compared  with  B.  t.  u.  11 
Carbon,  amount  of  air  to  burn  26 

dioxide  defined  36 

dioxide  exhaled  42 

dioxide  in  air  36 

dioxide,  tests  for  33,  38 
Carpenter,  Prof.  B.  C.  71,  259 
Central  Station  heating,  See  district 

heating  275 

Centrifugal  pumps  207,  315 
Charles'  law  25 
Chimney  applications  58 

area,  determination  of  57 
Chimneys  59 

capacity  of  422 
Coal,  fuel  values  of  421 
Coils,  arrangement  of  in  pipe  heater 
153,  179,  221,  245 

aspirating  176 

blower  system  240 

direct  radiation  153 

heat  transmission  through  167,  240 

sq.  ft.  for  cooling  381 


471 


472 


INDEX 


surface,  plenum  system  240 

temp,  leaving"  Vento  239 
Cold  air  system  of  refrig.  355 
Combination  systems  103,  149,  224 
Combustion  of  fuels  26 
Comparison  of  furnace  and  other 

systems  76 

Compression  system  of  refrig.  356 
Condensation,  dripping-  from  mains 
143,  338 

return  to  boilers  193 
Condenser,  concentric  tube  359 

enclosed  360 

.exhaust  steam  306 

for  compression  systems  359 

heating  surface  in  307 

submerged  360 
Conduction  18,  62 
Conductivities  of  building  material 
63,  65 

of  radiating-  surfaces  154,  167 
Conduits,  district  heating  279 
Convection  18,  62 

heat  loss  due  to  62,  67,  72 
Conversion  factors  for  water  411 
Coolers  for  weak  liquor  371 
Cost  of,   heating   from   central   sta- 
tion 326 

ice  making  385,  460 
Cowls  and  vent,  heads  60 
Cripps  system  137 

Designs,  typical- 
central  station  289,  327 

furnace  86 

hot  water  185 

plenum  267 
Dew  point,  influence  of  on  refrig.  375 

temperature  of  air  48 
Dew  points  of  air  418 
Direct-indirect  radiation  170 
Direct  radiation,  tapping  list  431 
Dirt  strainer,  Webster  207 
District  heating  275 

adaptation  to  private  plants  338 

amount  of  radiation  supplied  by 
one  horse-power  exhaust  steam 
306,  339 

amount  of  radiation  supplied  298 

amount  of  radiation  supplied  by 
reheater  310 

application  to  typical  design  289 

boiler  feed  pumps  317 

boilers  319 

capacity  of  boiler  plant  323 

centrifugal  pumps  315 

circulating  pumps  313 

city  water  supply  317 

classification  295 

conduits  279 

cost  of  heating  326 

cost,  summary  of  tests  328 

diameter  of  mains  302,  334 

dripping  condensation  from  mains 
338 


economizer  321 

exhaust  steam  available  304 

future  increase  298 

heat  available  in  exhaust  steam  292 

heating-  surface  in  reheater  307 

high  pressure  steam  heater  312 

hot  water  systems  295 

layout  for  conduit  mains  285 

power  plant  layout  327,  333 

pressure  drop  in  mains  334 

radiation  in  district  298 

radiation  supplied  by  1  h.  p.  of  ex. 

st.  306,  :«!> 

radiat'n  supplied  by  economizer  321 
radiat'n  supplied  per  boiler  h.  p.  320 
regulation  331 
reheater  details  310 
reheater  for  circulating  water  307 
reheater  tube  surface  308 
service  connections  303 
steam  available  for  heating-  290 
systems  classified  295 
typical  design  for  consideration  289 
velocity  of  water  in  mains  312 
water  per  hr.,  as  heat  medium  297 
water  to  condense  one  pound  of 
steam  305 

Double  duct,  plenum  system  229 

Ducts,  furnace  system  106 
plenum  system  237,  268,  272 

Dunham  system  135,  203 

Economizers  321 
Efficiencies  of  boilers  31,  320 

of  furnaces  31,  84 

radiation  supplied  by  321 

surface  323 
Electric  pumps  197 
Electrical  heating  350 

future  of  352 
Engine,  size  of  for  plenum  system  264 

water  rate  306,  310 
Estimating-,  data  for  466 
Evaporators  for  refrig.  361 
Exchangers  371 

Exhaust  steam  heating  201,  248,  266, 
277,  292,  339 

condensers  306 

radiation  supplied  306 

steam  available  304 
Expansion  joints  287 

tanks  163,  439 
Exposure  heat 


Factors  of  evaporation  447 
Fan-coil  system,  See  plenum  system. 

furnace  system  113 
Fans  and  blowers  214 

capacity  450,  451,  452 

drives  262 

housings  217 

power  of  engine  for  264 

selection  of  fan  for  cap.  261 

sizes,  approx.  260 

speed  of  263 


INDEX 


473 


Filtering,   washing   and   humidifying 

air  46,  95.  230 
Fittings,  steam  and  hot  water  157 

table  of  sizes  440 
Flue  gas  analysis  17 
Freezing  mixtures  454 
Fresh  air  duct  83,  106,  218 
Fresh  air  inlet  to  bldgs.  218 
Friction  diagrams,  water  442,  443 

in  water  pipes  438 

of  air  in  pipes  441 

of  steam  in  pipes  334 
Fuel  values  of  Am.  coals  421 
Fuels,  combustion  of  26. 
Furnace  heating  76 

air  circulation  within  room  78,  113 

foundations  105 

location  and  setting  105 

pipeless  104 

selection  100 

sizes  424,  425 
Furnace  system,  fan  113 
Furnace  system,  gravity  76 

accelerating  circulation  117 

air  required  as  heat  carrier  70 

design  of  86 

efficiencies  31,  81 

essentials  of  77 

fresh  air  duct  in  83 

grate  area  in  84 

gross  register  area  in  81 

heat  stacks,  sizes  of  82 

heating  surface  in  85 

leader  pipes  in  83 

net  vent  register  in  81 

plans  for  89 

points  to  be  calculated  in  77 
•   register  temperature  80 

registers  80,  109 

stacks  or  risers  in  82,  110 

suggestions  for  operating  118 

vent  stacks  83 

Gage  pressure  15 
Gallon  degree  calculation  383 
Gas  analysis  32 
Gas-steam  systems  140 
Generators  368 

Honeywell  heat  137 
Grate  area,  boilers   and  heaters   144, 
166 

furnaces  84 
Greenhouse  heating  177 

Hammer,  water  192 

Hawkes  system  116 

Heat  10 

application  to  solids  and  liquids  20 
application  to  gases  24 
given  off  by  combustion  26 
given  off  by  persons,  lights,  etc.  74 
given  off  by  radiators  154 
latent  15 

mech.  equivalent  of  15 
specific  16 


Heat  loss,  chart  65 

combined  with  vent,  losses  73 

for  a  10  room  house  88 

for  average  year  94 

method  of  estimating  69-73 
Heat  losses  from  bldg.  materials  63 

due  to  conduction  61 

due  to  convection  67 

due  to  radiation  63 

due  to  exposure  69 
Heaters,  combination  103,  149 

hot  water  144 
Heating,  boilers  319 

capacity,   performance   to    guaran- 
tee 74 

district  275 

electric  350 

furnace  76 

hot  water  and  steam  120 

mech.  vacuum  200 

plenum  213 

surface  in  boilers  148,  320 

surface  in  coils  240 

surface  in  economizer  323 

surface  in  reheater  307,  30!) 

systems,  comparison  of  76,  120,  200, 

213 
High  pressure  heater  312 

velocity  h.  w.  systems  137 
Honeywell  sys.  137 
Horse-power,  in  moving  air  257 

of  boilers  320 

of  engine  264 

of  fan  259 
Hot-air  pipes,  cap.  of  424 

air  radiator  systems  115 

ducts  83 

stacks  82 
Hot  water  and  steam  heating  120 

accelerated  or  high  press,  h.  w.  sys- 
tems 136 

calculation  of  rad.  sur.  167 

classifications  121-124 

connection    to    radiators    128,    153, 
173,  185,  431 

design,  h.  w.  185 

determination  of  pipe  sizes  180,  334 

diagrams  for  125 

empirical  equations  170 

expansion  tanks  163 

fittings  157 

for  district  service  275 

for  tanks  and  pools  198 

grate  area  148,  166 

greenhouse  radiation  178 

location  of  radiators  for  185 

main  and  riser  layouts  126,  182,  188, 
191 

pipes,  tables  of  sizes  430 

pitch  of  mains  for  184 

principles  of  design  of  166 

radiators*  150 

risers,  capacity  table  433,  434,  435 

proportioning  pipe  sizes  182 

suggestions  for  operating  199 


474 


INDEX 


sys.,  accelerated  or  high  vel.  136 

systems,  h.  w.  and  st.  125 

systems,  vapor  130 

temperature  331 

water  used  in  indirect  coils  -247 
Housing,  effect  on  radiators  155 
Humidity,  abs.  rel.  46 

effect  upon  persons  44 

tables  of  416,  417 
Hydrometric  scales  compared  462 
Hygrodeik  47 
Hygrometer  46,  48 
Hygrometric  chart  49 

Ice  making  and  refrig,  356,  384 

capacity,  calculation  384 

cost  of  385 
Illinois  sys.  135 
Indirect  radiators  122,  173 
Insulation  of  st.  and  h.  w.  pipes  191, 
279 

(K)  values  for  coils,  radiators  154,  241 
Koerting  system  138 

Latent  heat  15 
Leader  pipes  83 
Location  of  furnaces  105 

of  radiators  185 

of  registers  103,  109,  112,  117 

of  stacks  82,  90,  110 

Main  and  riser  layout  126,   182,  184, 

188,  191 
Mains,  cap.  of  hot  water  180,  433,,  434 

cap.  of  steam  180,  334,  435-437 

condensation  from  181,  338 

diameter  of,  calculation  180,  334 

pitch  of  184 

pressure  drop  and  diam.  of  299,  334 

velocity  of  water  in  302 
Manholes  289 
Measurement  of  air  velocities  54,  249 

of  temperatures  10 
Mechanical  equivalent  of  heat  15 
Mechanical  vacuum  sys.  200 

advantages  of  200 

Automatic.    Bishop    and    Babcock, 
Dunham,  Illinois,  Webster  203 

dirt  strainers  for  206,  207 

pump  capacities  for  206,  208 

radiation  for  169 

regulation  for  206 

return  line  valves  for  209,  210 
Mechanical  warm  air  sys.     See  Ple- 
num sys. 

Mills  system  (attic  main)  127 
Moisture,  addition  of,  to  air  51 

effect  upon  persons  44 
Moline  sys.  134 
Mouat-Squires  sys.  133 

Naperian  logarithms  411 
Nitrogen  36 
(n)  values  of  71 


Operation  of  furnaces  118 
of  hot  water  heaters  and  steam 

boilers  199 

Outside  temp,  for  design  92 
Oxygen  36 

Paul  system  203 

piping  connections  for  204 
Performance  to  guarantee  heating 

capacity  74 
Pipe,  coil  radiators  153,  179,  221,  245 

connections  266 

equalization  of  sizes  432 

fittings  141,  157,  440 

for  refrigeration  363 

leader  83 

line  refrigeration  376 

sizes,  determination  of  180,  182,  302, 

334 

Pipeless  furnace  104 
Pipes,  capacities  of  433-437 

for  refrigeration  363 
Piping  connection  around  heater  and 
engine  266 

corrosion  of  piping  165 

for  heating  sys,  definitions  120-128 

system    for    automatic   control   of 

vacuum  206 
Pitot  tubes  55,  255 
Plans,  and  specifications  388 

of  typical  Cent,  station  327 

of  typical  furnace  sys.  89 

of  typical  hot  water  sys.  188 

of  typical  plenum  sys.  268 
Plenum  system,  mech.  warm  air  sys. 
213 

air  needed  cu.  ft.  per  hour  in  235 

air  velocity  237 

air  velocity,  theoretical  249 

air  washing  and  humidifying  230 

amount  of  steam  condensed  248 

application  of  to  school  bldgs.  267 

approximate  rules  for  244,  254,  259 

approximate  sizes  of  fan  wheels  260 

arrangement  of  coils  in  pipe  heat- 
ers 245 

arrangement  of  sees,  and  stacks  in 
Vento  heaters  246 

blower  fans,  actual  h.  p.  to  move 
air  257 

Carpenter's  rules  for  259 

cast  surface  for  223 

coil  surface  in  240 

cross  sectional  area  ducts,  regis- 
ters, etc.  237 

data  267 

division  of  coil  surface  in  223 

double  ducts  in  229 

dry  steam  needed  in  excess  of  exh. 
from  engine  248 

efficiency  and  air  temp.  236,  239-242 

factors  for  change  of  velocity  and 
volume  251-253 

fan  drives  for  262 

final  air  temperature  in  236,  238 


INDEX 


475 


floor  plans  for  268-274 

heating  surface  in  coils  of  240 

heating  surfaces  220 

h.  p.  of  engine  for  fan  for  264 

h.  p.  to  move  air  253,  257-260 

(K)  values  of  154,  241 

piping   connections    around   heater 
and  engine  266 

pressure  and  velocity,  results  of 
tests  of  254 

single  duct  in  228 

speed  of  fans  for  263 

split  system  228,  271 

temp,  of  air  at  register  236 

temp,  of  air  leaving  coils  238 

total  heat  loss  per  hour  235,  267 

use  of  hot  water  in  indirect  coils  247 

vel.  of  air  escaping  to  atmos.  252 

work  done  in  moving  air  257 
Pools,  heating  water  for  198 
Power,  definition  19 

plant  layout  327,  333 
Pressed  steel  radiators  150,  158 
Pressure,  absolute  15 

and  velocity,  results  of  tests  254 

gage  15 

in  water  mains  298 
Properties  of  air  417 

of  ammonia  454 

of  carbon  dioxide  456 

of  steami  407 

of  sulphur  dioxide  456 
Psychrometer,  sling  48 
Psychrometric  chart  418 
Pumps,  boiler  feed  197,  317 

centrifugal  207,  315 

circulating  313 

city  water  supply  317 

electric  197 

for  absorption  system  371 

power  required  for  314-319 

steam  needed  for  294 
Purification  of  air  43: 

Radiation  17 

amount   of,    one  sq.    ft.    reheater 
tube  surface  will  supply  310 

amt.  supplied  by  one  h.  p.  306 

amt.  supplied  by  economizer  321 

direct-indirect  170 

indirect  122,  173 

hot  water  and  steam  167 

one  Ib.  exh.  steam  will  supply  305 

sur.  to  heat  circulating  water  306 
Radiators,  amt.  of  surface  on  158 

cast  150,  158,  223 

classification  of  150 

direct  121 

direct-indirect  121 

effect  of  housing  155 

hot-air,  systems  115 

indirect  122 

location  and  connection  of  185 

pipe  coil  150,  221 

pressed  steel  150,  158 


sizes  158,  173 

sizes,  etc.,  for  ten  room  house  187 

surface  calculation  for  167 

surface  effect  on  trans,  of  heat  154 

tapping  list  431,  433 
Reck  system  139 
Rectifiers  368 
Rector  system  115 
Refrigeration  353 

absorbers  370 

absorption  system,  elevation  of  366 

capacities  459 

capacity  of  brine  cooled  system  385 

circulating  system  372 

classification  of  systems  353 

coils,  sq.  ft.  cooling  381 

cold  air  system  355 

comparison  of  systems  372 

compression  system  355 

condenser  369 

coolers  for  weak  liquor  371 

costs  of  ice  making  385,  460 

evaporators  361 

exchangers  371 

gallon  degree  calculation  385 

general  application  383 

generators  368 

heat  loss  379 

horse-power  for  458 

ice  making  cap.  calculation  384 

influence  of  dew  point  375 

methods  of  maintaining  low  temp. 
375 

pipe  line  376 

pipes,  valves  and  fittings  363 

pump  for  absorption  system  371 

rectifiers  368 

vacuum  system  354 
Register,  area  of  81,  423,  424 

connections  109 

inlets  219 

temperatures  80,  237 
Regulation,  district  heating  331 

damper  219,  225 

large  plants  343 

small  plants  341 
Room  temperatures,  standard  73 

Salt  brine  solution  458 
Service  connections  288,  303 
Sheet  metal  dimensions  426 
Single  duct,  plenum  system  228 
Sizes,  of  fan  wheels,  approximate  260 

of  ice  cans  463 

Smoke  flues,  equalization  of  423 
Specific  heat  16 

heats,  etc.,  of  substances  428 
Specifications  for  plans  388 

for  boilers  145,  187 
Speeds  of  blower  fans  263 
Split  sys.  plenum  heating  228,  271 
Splitters  219 
Squares,  cubes,  etc.  400 
Stacks  and  risers  82,  110 


INDEX 


Strain,  nncl   hoi   water  heating  120 
See  also  h.  \v.  and  st.  lioat. 

amt.  condensed  in  plenum  sys.  248 

available  for  heating  circulating 
water  304 

boilers  319 

calculation  of  rad.  sur.  167 

classifications  121-124 

connection  to  radiators  128,  153,  173, 
185,  431 

condensed   per   sq.    ft.    of    heating 
sur.  per  hour  182,  248 

determination  of  pipe  sizes  180,  334 

diagrams  for  125 

dry,  needed  in  excess  of  engine  ex- 
haust 248,  290-295,  339 

empirical  equations  170 

fittings  157 

gas-system  140 

grate  area  148,  166 

greenhouse  rad.  178 

heater,  high  pressure  312 

heating,  district  289,  298 

location  of  radiators  for  185 

loop  195 

main  and  riser  layouts  126,  182 

mains,  diameter  of  334,  435-437 

pipe  insulation  191,  279 

pipe  sizes,  table  of  430 

pitch  of  the  mains  for  184 

principles  of  design  of  166 

properties  of  sat.  407 

proportioning  pipe  sizes  182 

radiators  150 

risers,  capacity  tables  433-435 

sealed  returns  128 

suggestions  for  operating  199 

systems,  h.  w.  and  st.  125 

systems,  vapor  130 

traps,  high  pressure  195 

used  by  engines  306,  310 
Street  mains  and  conduits,  layout  285 
Suggestions   for   operating,   furnaces 
118 

for  school  districts  395 

for  specifications  388 

hot  water  heaters  and  boilers  199 
Sylphon  damper  regulator  136,  149 
Systems,   comparison  of  heating  76, 
120,  200,  213 

Table  I  radiation  constants  17 
Table  II  determination  of  CO2  40 
Tables  III,  IV  volume  of  air  per  per- 
son 42 

Table  V  ave.  temp,  chimney  gases  54 
Table  VI  values  of  (K)  63 
Table  VII  exposure  losses  69 
Table  VIII  values  of  (n)  71 
Table  IX  standard  room  temps.  73 
Table  X  temps,  unheated  rooms  73 
Table  XI  heat  given  off  by  persons, 

lights,  etc.  74 

Table  XII  calculations  for  10  room 
house  88 


Table  XIII  radiator  surfaces  158 
Table  XIV  indirect  rad,  sur.  \T.i 
Table  XV  cap.  of  indirect  rarLs.  174 
Table  XVI  cap.  greenhouse  rad'n   ITS 
Tables  XVII,  XVIII,  XIX  proportion- 
ing pipe  sizes  183 
Table  XX  cal.  data  for  10  room 

house  187 

Table  XXI  cap.  Marsh  vac.  pumps  2<x> 
Table  XXII  cap.  Nash  vac.  pumps 

208 

Table  XXIII  sur.  Vento  heaters  224 
Table  XXIV  plenum  air  vel.  237 
Table  XXV  temps,  leaving  steam 

coils  239 
Table  XXVI  temps,  leaving  Vento 

coils  239 

Table  XXVII  values  of  (c)  241 
Table  XXVIII  efficiencies  of  coil 

heaters  241 

Table  XXIX  efficiencies  of  coil  heat- 
ers 242 

Table  XXX  air  pressure  vel.  251 
Table  XXXI  air  pressure,  vel.  252 
Table  XXXII  air  pressure,  vel.  253 
Table  XXXIII  approx.  fan  sizes  260 
Table  XXXIV  fans  speed  ->M 
Table  XXXV  cal.  data  for  school 

buildings  267 
Table  XXXVI  heat  loss  from  conduit 

mains  284 
Tables  XXXVII,  XXXVIII  friction 

loss  in  conduit  mains  301,  302 
Table  XXXIX  diameeters  of  conduit 

mains  340 

Table  XL  heat  loss  through   insula- 
tion 379 

Table  1  squares,  cubes,  etc.  400 
Table  2  trigonometric  functions  406 
Table  3  equivalents  of  units  406 
Table  4  properties  of  steam  407 
Table  5  Naperian  logarithms  411 
Table  6  water  conversion  factors  411 
Table  7  vol.  and  wt.  of  dry  air  412 
Table  8  Boiling  temp,  at  different 

elevation  412 

Table    9  weight  of  pure  water  413 
Table  10  boiling  points   of  water  in 

vacuum  415 

Table  11  wt.  of  water  and  air  415 
Table  12  relative  humidities  416 
Table  13  properties  of  air  417 
Table  14  dew  points  of  air  418 
Table  15  fuel  value  of  Am.  coals  421 
Table  16  capacities  of  chimneys  422 
Table  17  Excelsior  Avail  stacks  422 
Table  18  equalization  of  smoke  flues 

423 

Table  19  dimensions  of  registers  423 
Table  20  cap.  of  furnaces  424 
Table  21  cap.  hot  air  pipes  and  regs. 

424 

Table  22  cap.  of  furnaces  425 
Table  23  area  of  vertical  hot  air 
flues  425 


INDEX 


477 


Table  -24  shirt  metal  sixes  I2<; 
Table  2.">  weight  of  <i.  1.  pipe  and  el- 
bows 427 
Table  20  sp.   ht.,  etc.,  of  substances 

428 

Tables  27,  28  water  pressures  at  vari- 
ous heads  420 

Table  29  wrought  iron  pipe  sizes  430 
Table  30  expansion  of  pipes  431 
Table  31  tapping  list  of  direct  rads. 

431 

Table  32  pipe  equalization  432 
Table  33  sizes  of  h.  w.  mains  433 
Table  34  Sizes  of  h.  w.  branches  and 

risers  433 
Table  35  sizes  of  h.  w.  rad.  tappings 

433 

Table  36  Honeywell  pipe  sizes  434 
Table  37  cap.  of  h.  w.  mains  and 

risers  434 

Table  38  cap.  of  st.  and  ret.  pipes  435 
Table  39  sizes  of  st.  mains  436 
Tqble  40  sizes  of  st.  and  ret.  lines  437 
Table  41  sizes  of  rad.  connections  437 
Table  42  friction  in  water  pipes  438 
Table  43  grav.  and  vac.  returns  439 
Table  44  expansion  tanks  439 
Table  45  sizes  of  flanged  fltgs.  440 
Table  46  sizes  of  pipe  fittings  440 
Table  47  friction  in  air  pipes  441 
Table  48  temp,  for  testing  steam 

plants  444 

Table  49  Kewanee  boilers  445 
Table  50  heat  trans,  through  pipe 

covering  446 

Table  51  factors  of  evap.  447 
Table  52  heat  in  feed  water  447 
Table  53  sizes  of  Vento  heaters  448 
Table  54  steam  used  by  engines  449 
Tables  55,  56,  57  speeds,  cap.,   h.   p. 

of  various   fans  450,   451, 

452 

Table  58  freezing  mixtures  454 
Table  59  properties  of  ammonia  454 
Table  60  sol.  of  ammonia  in  water 

455 
Table  61  strength  of  ammonia  liquor 

455 

Table  02  prop,  of  sulphur  dioxide  456 
Table  63  prop,  of  carbon  dioxide  456 
Table  04  boiling  points  of  liquids  457 
Table  05  calcium  brine  sol.  457 
Table  66  salt  brine  sol.  458 
Table  67  horse-power  for  refrig.  458 
Table  68  ammonia  for  one-ton  refrig. 

459 

Table  69  refrigeration  caps.  459 
Table  70  cost  of  ice  making  460 
Table  71  temp,  of  ammonia  under 

comp.  461 
Table  72  comparison    of   hydrometer 

scales  462 

Table  73  time  req'd  to  freeze  ice  463 
Table  74  sizes  of  ice  cans  463 


Table  75  req'd  temp.  Tor  cold  storage 

463 

Tanks,  expansion  163 
Temperature  absolute  14 

best  outside  for  design  92 

chart  93 

Tapping  list  for  direct  rad.  431,  433 
Temp,  control,  in  heating  sys.  341 

important  points  in  344 

in  large  plants  343 

in  small  plants  342 

Johnson,  National  Powers  sys. 

345-349 
Temperatures,  absolute  14 

best  to  use  in  heat  calculation  73 

for  cold  storage  463 

for  testing  plants  444 

of  air  and  rad.  in  greenhouses  178 

of  air  entering  rooms  80,  236 

of  air  leaving  coils  in  plenum  sys- 
tem 239,  242 

of  ammonia  under  comp.  461 

measurement  of  high  11 

methods  of  maintaining  low  373 

standard  room  73 

Tests  to  guarantee  heat  capacity  74 
Thermometers  11 

wet  and  dry  bulb  for  hygrometer  48 
Thermostat  342,  346 
Thermostatic  valves  209,  228 
Time  reg.  to  freeze  ice  463 
Traps,  steam  194,  195 
Trigonometric  functions  406 

Under-feed  furnaces  102 

Use  of  hot  water  in  indirect  coils  247 

Vacuum  and  gravity  returns  com- 
pared 439 
Vacuum  sys.  steam  130,  200 

of  refrigeration  354 
Values  of  (K)  63,  154,  167,  241 

of  (n)  71 
Valves,  air  161 

check  161 

main  supply  159 

radiator  supply  160 

return  line  automatic  209,  210 

thermostatic  209,  228 
Vapor,  atmospheric  and,  sys.  130 
Velocity  of  air  by  appl.  of  heat  52 

of  air  escaping  to  atmosphere  252 
Vent.,  heads  and  cowls  60 

registers  (net)  81 

stacks  83 
Ventilation,  defined  43 

air  required  per  person  40 

heat  loss  72 
Vento  heaters  223,  224,  239 

sizes  448 

Vertical  hot  air  flues  425 
Volume  and  wt.  of  air  412,  415 


478 


INDEX 


Warm  air  fur.,  cap.  of  424,  425 
Washing  and  humidifying  air  46.  95, 

230 
Water,  conversion  factors  411 

hammer  192 

height  of  column  corresponding  to 
pressures  in  ounces  429 

needed  per  hour  in  dist.  heatg.  297 

pressure  in  mains  298 

sealed  returns  128 

weight  of  pure  413,  414 


weight  of,  and  air  415 
Webster  sys.  135,  203 
Weight,  and  sizes  of  sheet  metal  42(> 

of  G.  I.  pipe  427 

of  pure  water  413,  414 

of  water  and  air  415 
Work,  definition  19 

done  in  moving  air  253,  257 
Wrought  iron  and  steel  pipe  sizes  430 

Zellweger  fan  232 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
This  boot  bdow. 


JUN  4       1946 


LD  21-100m-9,'47(A5702sl6)476 


YB  24 


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UNIVERSITY  OF  CALIFORNIA  LIBRARY 


